diff --git a/core/field.ts b/core/field.ts
index 8f4fa456d..ba1de9ef2 100644
--- a/core/field.ts
+++ b/core/field.ts
@@ -209,7 +209,7 @@ export abstract class Field implements IASTNodeLocationSvg,
    */
   constructor(
       value: AnyDuringMigration, opt_validator?: Function|null,
-      opt_config?: AnyDuringMigration) {
+      opt_config?: FieldConfig) {
     /**
      * A generic value possessed by the field.
      * Should generally be non-null, only null when the field is created.
@@ -237,17 +237,14 @@ export abstract class Field implements IASTNodeLocationSvg,
    *     individual field's documentation for a list of properties this
    *     parameter supports.
    */
-  protected configure_(config: AnyDuringMigration) {
-    let tooltip = config['tooltip'];
-    if (typeof tooltip === 'string') {
-      tooltip = parsing.replaceMessageReferences(config['tooltip']);
+  protected configure_(config: FieldConfig) {
+    // TODO (#2884): Possibly add CSS class config option.
+    // TODO (#2885): Possibly add cursor config option.
+    if (config.tooltip) {
+      this.setTooltip(parsing.replaceMessageReferences(config.tooltip));
     }
-    tooltip && this.setTooltip(tooltip);
   }
 
-  // TODO (#2884): Possibly add CSS class config option.
-  // TODO (#2885): Possibly add cursor config option.
-
   /**
    * Attach this field to a block.
    * @param block The block containing this field.
@@ -1200,3 +1197,10 @@ export abstract class Field implements IASTNodeLocationSvg,
     }
   }
 }
+
+/**
+ * Extra configuration options for the base field.
+ */
+export interface FieldConfig {
+  tooltip?: string;
+}
diff --git a/core/field_angle.ts b/core/field_angle.ts
index 1f3880b30..f313ee6ba 100644
--- a/core/field_angle.ts
+++ b/core/field_angle.ts
@@ -21,7 +21,7 @@ import * as Css from './css.js';
 import * as dropDownDiv from './dropdowndiv.js';
 import {Field} from './field.js';
 import * as fieldRegistry from './field_registry.js';
-import {FieldTextInput} from './field_textinput.js';
+import {FieldTextInputConfig, FieldTextInput} from './field_textinput.js';
 import * as dom from './utils/dom.js';
 import {KeyCodes} from './utils/keycodes.js';
 import * as math from './utils/math.js';
@@ -121,7 +121,7 @@ export class FieldAngle extends FieldTextInput {
    */
   constructor(
       opt_value?: string|number|Sentinel, opt_validator?: Function,
-      opt_config?: AnyDuringMigration) {
+      opt_config?: FieldAngleConfig) {
     super(Field.SKIP_SETUP);
 
     /**
@@ -165,15 +165,15 @@ export class FieldAngle extends FieldTextInput {
    * Configure the field based on the given map of options.
    * @param config A map of options to configure the field based on.
    */
-  override configure_(config: AnyDuringMigration) {
+  protected override configure_(config: FieldAngleConfig) {
     super.configure_(config);
 
-    switch (config['mode']) {
-      case 'compass':
+    switch (config.mode) {
+      case Mode.COMPASS:
         this.clockwise_ = true;
         this.offset_ = 90;
         break;
-      case 'protractor':
+      case Mode.PROTRACTOR:
         // This is the default mode, so we could do nothing. But just to
         // future-proof, we'll set it anyway.
         this.clockwise_ = false;
@@ -182,33 +182,10 @@ export class FieldAngle extends FieldTextInput {
     }
 
     // Allow individual settings to override the mode setting.
-    const clockwise = config['clockwise'];
-    if (typeof clockwise === 'boolean') {
-      this.clockwise_ = clockwise;
-    }
-
-    // If these are passed as null then we should leave them on the default.
-    let offset = config['offset'];
-    if (offset !== null) {
-      offset = Number(offset);
-      if (!isNaN(offset)) {
-        this.offset_ = offset;
-      }
-    }
-    let wrap = config['wrap'];
-    if (wrap !== null) {
-      wrap = Number(wrap);
-      if (!isNaN(wrap)) {
-        this.wrap_ = wrap;
-      }
-    }
-    let round = config['round'];
-    if (round !== null) {
-      round = Number(round);
-      if (!isNaN(round)) {
-        this.round_ = round;
-      }
-    }
+    if (config.clockwise) this.clockwise_ = config.clockwise;
+    if (config.offset) this.offset_ = config.offset;
+    if (config.wrap) this.wrap_ = config.wrap;
+    if (config.round) this.round_ = config.round;
   }
 
   /**
@@ -509,10 +486,10 @@ export class FieldAngle extends FieldTextInput {
    * @nocollapse
    * @internal
    */
-  static override fromJson(options: AnyDuringMigration): FieldAngle {
+  static override fromJson(options: FieldAngleFromJsonConfig): FieldAngle {
     // `this` might be a subclass of FieldAngle if that class doesn't override
     // the static fromJson method.
-    return new this(options['angle'], undefined, options);
+    return new this(options.angle, undefined, options);
   }
 }
 
@@ -546,4 +523,41 @@ Css.register(`
 
 fieldRegistry.register('field_angle', FieldAngle);
 
-(FieldAngle.prototype as AnyDuringMigration).DEFAULT_VALUE = 0;
\ No newline at end of file
+(FieldAngle.prototype as AnyDuringMigration).DEFAULT_VALUE = 0;
+
+/**
+ * The two main modes of the angle field.
+ * Compass specifies:
+ *   - clockwise: true
+ *   - offset: 90
+ *   - wrap: 0
+ *   - round: 15
+ *
+ * Protractor specifies:
+ *   - clockwise: false
+ *   - offset: 0
+ *   - wrap: 0
+ *   - round: 15
+ */
+export enum Mode {
+  COMPASS = 'compass',
+  PROTRACTOR = 'protractor',
+}
+
+/**
+ * Extra configuration options for the angle field.
+ */
+export interface FieldAngleConfig extends FieldTextInputConfig {
+  mode?: Mode;
+  clockwise?: boolean;
+  offset?: number;
+  wrap?: number;
+  round?: number;
+}
+
+/**
+ * fromJson configuration options for the angle field.
+ */
+export interface FieldAngleFromJsonConfig extends FieldAngleConfig {
+  angle?: number;
+}
diff --git a/core/field_checkbox.ts b/core/field_checkbox.ts
index b4eb49127..e1ad4bcfd 100644
--- a/core/field_checkbox.ts
+++ b/core/field_checkbox.ts
@@ -18,7 +18,7 @@ goog.declareModuleId('Blockly.FieldCheckbox');
 // Unused import preserved for side-effects. Remove if unneeded.
 import './events/events_block_change.js';
 
-import {Field} from './field.js';
+import {FieldConfig, Field} from './field.js';
 import * as fieldRegistry from './field_registry.js';
 import * as dom from './utils/dom.js';
 import type {Sentinel} from './utils/sentinel.js';
@@ -61,7 +61,7 @@ export class FieldCheckbox extends Field {
    */
   constructor(
       opt_value?: string|boolean|Sentinel, opt_validator?: Function,
-      opt_config?: AnyDuringMigration) {
+      opt_config?: FieldCheckboxConfig) {
     super(Field.SKIP_SETUP);
 
     /**
@@ -86,11 +86,9 @@ export class FieldCheckbox extends Field {
    * Configure the field based on the given map of options.
    * @param config A map of options to configure the field based on.
    */
-  protected override configure_(config: AnyDuringMigration) {
+  protected override configure_(config: FieldCheckboxConfig) {
     super.configure_(config);
-    if (config['checkCharacter']) {
-      this.checkChar_ = config['checkCharacter'];
-    }
+    if (config.checkCharacter) this.checkChar_ = config.checkCharacter;
   }
 
   /**
@@ -219,13 +217,27 @@ export class FieldCheckbox extends Field {
    * @nocollapse
    * @internal
    */
-  static fromJson(options: AnyDuringMigration): FieldCheckbox {
+  static fromJson(options: FieldCheckboxFromJsonConfig): FieldCheckbox {
     // `this` might be a subclass of FieldCheckbox if that class doesn't
     // 'override' the static fromJson method.
-    return new this(options['checked'], undefined, options);
+    return new this(options.checked, undefined, options);
   }
 }
 
 fieldRegistry.register('field_checkbox', FieldCheckbox);
 
-(FieldCheckbox.prototype as AnyDuringMigration).DEFAULT_VALUE = false;
\ No newline at end of file
+(FieldCheckbox.prototype as AnyDuringMigration).DEFAULT_VALUE = false;
+
+/**
+ * Config options for the checkbox field.
+ */
+export interface FieldCheckboxConfig extends FieldConfig {
+  checkCharacter?: string;
+}
+
+/**
+ * fromJson config options for the checkbox field.
+ */
+export interface FieldCheckboxFromJsonConfig extends FieldCheckboxConfig {
+  checked?: boolean;
+}
diff --git a/core/field_colour.ts b/core/field_colour.ts
index 354f7f8c3..0e91e8a19 100644
--- a/core/field_colour.ts
+++ b/core/field_colour.ts
@@ -22,7 +22,7 @@ import {BlockSvg} from './block_svg.js';
 import * as browserEvents from './browser_events.js';
 import * as Css from './css.js';
 import * as dropDownDiv from './dropdowndiv.js';
-import {Field} from './field.js';
+import {FieldConfig, Field} from './field.js';
 import * as fieldRegistry from './field_registry.js';
 import * as aria from './utils/aria.js';
 import * as colour from './utils/colour.js';
@@ -155,7 +155,7 @@ export class FieldColour extends Field {
    */
   constructor(
       opt_value?: string|Sentinel, opt_validator?: Function,
-      opt_config?: AnyDuringMigration) {
+      opt_config?: FieldColourConfig) {
     super(Field.SKIP_SETUP);
 
     if (opt_value === Field.SKIP_SETUP) {
@@ -174,15 +174,11 @@ export class FieldColour extends Field {
    * Configure the field based on the given map of options.
    * @param config A map of options to configure the field based on.
    */
-  protected override configure_(config: AnyDuringMigration) {
+  protected override configure_(config: FieldColourConfig) {
     super.configure_(config);
-    if (config['colourOptions']) {
-      this.colours_ = config['colourOptions'];
-      this.titles_ = config['colourTitles'];
-    }
-    if (config['columns']) {
-      this.columns_ = config['columns'];
-    }
+    if (config.colourOptions) this.colours_ = config.colourOptions;
+    if (config.colourTitles) this.titles_ = config.colourTitles;
+    if (config.columns) this.columns_ = config.columns;
   }
 
   /**
@@ -572,7 +568,7 @@ export class FieldColour extends Field {
    * @nocollapse
    * @internal
    */
-  static fromJson(options: AnyDuringMigration): FieldColour {
+  static fromJson(options: FieldColourFromJsonConfig): FieldColour {
     // `this` might be a subclass of FieldColour if that class doesn't override
     // the static fromJson method.
     return new this(options['colour'], undefined, options);
@@ -618,3 +614,19 @@ Css.register(`
 `);
 
 fieldRegistry.register('field_colour', FieldColour);
+
+/**
+ * Config options for the colour field.
+ */
+export interface FieldColourConfig extends FieldConfig {
+  colourOptions?: string[];
+  colourTitles?: string[];
+  columns?: number;
+}
+
+/**
+ * fromJson config options for the colour field.
+ */
+export interface FieldColourFromJsonConfig extends FieldColourConfig {
+  colour?: string;
+}
diff --git a/core/field_dropdown.ts b/core/field_dropdown.ts
index b864385e6..ffb2b6195 100644
--- a/core/field_dropdown.ts
+++ b/core/field_dropdown.ts
@@ -21,7 +21,7 @@ goog.declareModuleId('Blockly.FieldDropdown');
 
 import type {BlockSvg} from './block_svg.js';
 import * as dropDownDiv from './dropdowndiv.js';
-import {Field} from './field.js';
+import {FieldConfig, Field} from './field.js';
 import * as fieldRegistry from './field_registry.js';
 import {Menu} from './menu.js';
 import {MenuItem} from './menuitem.js';
@@ -117,7 +117,7 @@ export class FieldDropdown extends Field {
    */
   constructor(
       menuGenerator: AnyDuringMigration[][]|Function|Sentinel,
-      opt_validator?: Function, opt_config?: AnyDuringMigration) {
+      opt_validator?: Function, opt_config?: FieldConfig) {
     super(Field.SKIP_SETUP);
 
     // If we pass SKIP_SETUP, don't do *anything* with the menu generator.
@@ -656,10 +656,16 @@ export class FieldDropdown extends Field {
    * @nocollapse
    * @internal
    */
-  static fromJson(options: AnyDuringMigration): FieldDropdown {
+  static fromJson(options: FieldDropdownFromJsonConfig): FieldDropdown {
+    if (!options.options) {
+      throw new Error(
+          'options are required for the dropdown field. The ' +
+          'options property must be assigned an array of ' +
+          '[humanReadableValue, languageNeutralValue] tuples.');
+    }
     // `this` might be a subclass of FieldDropdown if that class doesn't
     // override the static fromJson method.
-    return new this(options['options'], undefined, options);
+    return new this(options.options, undefined, options);
   }
 
   /**
@@ -686,14 +692,30 @@ export class FieldDropdown extends Field {
   }
 }
 
-/** Dropdown image properties. */
-interface ImageProperties {
+/**
+ * Definition of a human-readable image dropdown option.
+ */
+export interface ImageProperties {
   src: string;
   alt: string;
   width: number;
   height: number;
 }
 
+/**
+ * An individual option in the dropdown menu. The first element is the human-
+ * readable value (text or image), and the second element is the language-
+ * neutral value.
+ */
+export type MenuOption = [string | ImageProperties, string];
+
+/**
+ * fromJson config for the dropdown field.
+ */
+export interface FieldDropdownFromJsonConfig extends FieldConfig {
+  options?: MenuOption[];
+}
+
 /**
  * The y offset from the top of the field to the top of the image, if an image
  * is selected.
diff --git a/core/field_image.ts b/core/field_image.ts
index 7e81de0be..cad0e6b1e 100644
--- a/core/field_image.ts
+++ b/core/field_image.ts
@@ -15,7 +15,7 @@
 import * as goog from '../closure/goog/goog.js';
 goog.declareModuleId('Blockly.FieldImage');
 
-import {Field} from './field.js';
+import {FieldConfig, Field} from './field.js';
 import * as fieldRegistry from './field_registry.js';
 import * as dom from './utils/dom.js';
 import * as parsing from './utils/parsing.js';
@@ -84,13 +84,9 @@ export class FieldImage extends Field {
   constructor(
       src: string|Sentinel, width: string|number, height: string|number,
       opt_alt?: string, opt_onClick?: (p1: FieldImage) => AnyDuringMigration,
-      opt_flipRtl?: boolean, opt_config?: AnyDuringMigration) {
+      opt_flipRtl?: boolean, opt_config?: FieldImageConfig) {
     super(Field.SKIP_SETUP);
 
-    // Return early.
-    if (!src) {
-      throw Error('Src value of an image field is required');
-    }
     const imageHeight = Number(parsing.replaceMessageReferences(height));
     const imageWidth = Number(parsing.replaceMessageReferences(width));
     if (isNaN(imageHeight) || isNaN(imageWidth)) {
@@ -133,10 +129,12 @@ export class FieldImage extends Field {
    * Configure the field based on the given map of options.
    * @param config A map of options to configure the field based on.
    */
-  protected override configure_(config: AnyDuringMigration) {
+  protected override configure_(config: FieldImageConfig) {
     super.configure_(config);
-    this.flipRtl_ = !!config['flipRtl'];
-    this.altText_ = parsing.replaceMessageReferences(config['alt']) || '';
+    if (config.flipRtl) this.flipRtl_ = config.flipRtl;
+    if (config.alt) {
+      this.altText_ = parsing.replaceMessageReferences(config.alt);
+    }
   }
 
   /**
@@ -248,15 +246,37 @@ export class FieldImage extends Field {
    * @nocollapse
    * @internal
    */
-  static fromJson(options: AnyDuringMigration): FieldImage {
+  static fromJson(options: FieldImageFromJsonConfig): FieldImage {
+    if (!options.src || !options.width || !options.height) {
+      throw new Error(
+          'src, width, and height values for an image field are' +
+          'required. The width and height must be non-zero.');
+    }
     // `this` might be a subclass of FieldImage if that class doesn't override
     // the static fromJson method.
     return new this(
-        options['src'], options['width'], options['height'], undefined,
-        undefined, undefined, options);
+        options.src, options.width, options.height, undefined, undefined,
+        undefined, options);
   }
 }
 
 fieldRegistry.register('field_image', FieldImage);
 
-(FieldImage.prototype as AnyDuringMigration).DEFAULT_VALUE = '';
\ No newline at end of file
+(FieldImage.prototype as AnyDuringMigration).DEFAULT_VALUE = '';
+
+/**
+ * Config options for the image field.
+ */
+export interface FieldImageConfig extends FieldConfig {
+  flipRtl?: boolean;
+  alt?: string;
+}
+
+/**
+ * fromJson config options for the colour field.
+ */
+export interface FieldImageFromJsonConfig extends FieldImageConfig {
+  src?: string;
+  width?: number;
+  height?: number;
+}
diff --git a/core/field_label.ts b/core/field_label.ts
index 0e03c11cb..f464fef6b 100644
--- a/core/field_label.ts
+++ b/core/field_label.ts
@@ -17,7 +17,7 @@
 import * as goog from '../closure/goog/goog.js';
 goog.declareModuleId('Blockly.FieldLabel');
 
-import {Field} from './field.js';
+import {FieldConfig, Field} from './field.js';
 import * as fieldRegistry from './field_registry.js';
 import * as dom from './utils/dom.js';
 import * as parsing from './utils/parsing.js';
@@ -52,7 +52,7 @@ export class FieldLabel extends Field {
    */
   constructor(
       opt_value?: string|Sentinel, opt_class?: string,
-      opt_config?: AnyDuringMigration) {
+      opt_config?: FieldLabelConfig) {
     super(Field.SKIP_SETUP);
 
     if (opt_value === Field.SKIP_SETUP) {
@@ -66,9 +66,9 @@ export class FieldLabel extends Field {
     this.setValue(opt_value);
   }
 
-  override configure_(config: AnyDuringMigration) {
+  protected override configure_(config: FieldLabelConfig) {
     super.configure_(config);
-    this.class_ = config['class'];
+    if (config.class) this.class_ = config.class;
   }
 
   /**
@@ -121,8 +121,8 @@ export class FieldLabel extends Field {
    * @nocollapse
    * @internal
    */
-  static fromJson(options: AnyDuringMigration): FieldLabel {
-    const text = parsing.replaceMessageReferences(options['text']);
+  static fromJson(options: FieldLabelFromJsonConfig): FieldLabel {
+    const text = parsing.replaceMessageReferences(options.text);
     // `this` might be a subclass of FieldLabel if that class doesn't override
     // the static fromJson method.
     return new this(text, undefined, options);
@@ -131,4 +131,22 @@ export class FieldLabel extends Field {
 
 fieldRegistry.register('field_label', FieldLabel);
 
-(FieldLabel.prototype as AnyDuringMigration).DEFAULT_VALUE = '';
\ No newline at end of file
+(FieldLabel.prototype as AnyDuringMigration).DEFAULT_VALUE = '';
+
+// clang-format off
+// Clang does not like the 'class' keyword being used as a property.
+/**
+ * Config options for the label field.
+ */
+export interface FieldLabelConfig extends FieldConfig {
+  class?: string;
+}
+// clang-format on
+
+
+/**
+ * fromJson config options for the label field.
+ */
+export interface FieldLabelFromJsonConfig extends FieldLabelConfig {
+  text?: string;
+}
diff --git a/core/field_label_serializable.ts b/core/field_label_serializable.ts
index 51b300b05..3ff52f262 100644
--- a/core/field_label_serializable.ts
+++ b/core/field_label_serializable.ts
@@ -19,7 +19,7 @@
 import * as goog from '../closure/goog/goog.js';
 goog.declareModuleId('Blockly.FieldLabelSerializable');
 
-import {FieldLabel} from './field_label.js';
+import {FieldLabelConfig, FieldLabelFromJsonConfig, FieldLabel} from './field_label.js';
 import * as fieldRegistry from './field_registry.js';
 import * as parsing from './utils/parsing.js';
 
@@ -52,7 +52,7 @@ export class FieldLabelSerializable extends FieldLabel {
    * for a list of properties this parameter supports.
    */
   constructor(
-      opt_value?: string, opt_class?: string, opt_config?: AnyDuringMigration) {
+      opt_value?: string, opt_class?: string, opt_config?: FieldLabelConfig) {
     super(String(opt_value ?? ''), opt_class, opt_config);
   }
 
@@ -64,9 +64,9 @@ export class FieldLabelSerializable extends FieldLabel {
    * @nocollapse
    * @internal
    */
-  static override fromJson(options: AnyDuringMigration):
+  static override fromJson(options: FieldLabelFromJsonConfig):
       FieldLabelSerializable {
-    const text = parsing.replaceMessageReferences(options['text']);
+    const text = parsing.replaceMessageReferences(options.text);
     // `this` might be a subclass of FieldLabelSerializable if that class
     // doesn't override the static fromJson method.
     return new this(text, undefined, options);
diff --git a/core/field_multilineinput.ts b/core/field_multilineinput.ts
index 55dcc4a85..7835816dd 100644
--- a/core/field_multilineinput.ts
+++ b/core/field_multilineinput.ts
@@ -18,7 +18,7 @@ goog.declareModuleId('Blockly.FieldMultilineInput');
 import * as Css from './css.js';
 import {Field} from './field.js';
 import * as fieldRegistry from './field_registry.js';
-import {FieldTextInput} from './field_textinput.js';
+import {FieldTextInputConfig, FieldTextInput} from './field_textinput.js';
 import * as aria from './utils/aria.js';
 import * as dom from './utils/dom.js';
 import {KeyCodes} from './utils/keycodes.js';
@@ -68,7 +68,7 @@ export class FieldMultilineInput extends FieldTextInput {
    */
   constructor(
       opt_value?: string|Sentinel, opt_validator?: Function,
-      opt_config?: AnyDuringMigration) {
+      opt_config?: FieldMultilineInputConfig) {
     super(Field.SKIP_SETUP);
 
     if (opt_value === Field.SKIP_SETUP) {
@@ -83,9 +83,9 @@ export class FieldMultilineInput extends FieldTextInput {
     }
   }
 
-  override configure_(config: AnyDuringMigration) {
+  protected override configure_(config: FieldMultilineInputConfig) {
     super.configure_(config);
-    config['maxLines'] && this.setMaxLines(config['maxLines']);
+    if (config.maxLines) this.setMaxLines(config.maxLines);
   }
 
   /**
@@ -424,8 +424,9 @@ export class FieldMultilineInput extends FieldTextInput {
    * @nocollapse
    * @internal
    */
-  static override fromJson(options: AnyDuringMigration): FieldMultilineInput {
-    const text = parsing.replaceMessageReferences(options['text']);
+  static override fromJson(options: FieldMultilineInputFromJsonConfig):
+      FieldMultilineInput {
+    const text = parsing.replaceMessageReferences(options.text);
     // `this` might be a subclass of FieldMultilineInput if that class doesn't
     // override the static fromJson method.
     return new this(text, undefined, options);
@@ -448,3 +449,18 @@ Css.register(`
 `);
 
 fieldRegistry.register('field_multilinetext', FieldMultilineInput);
+
+/**
+ * Config options for the multiline input field.
+ */
+export interface FieldMultilineInputConfig extends FieldTextInputConfig {
+  maxLines?: number;
+}
+
+/**
+ * fromJson config options for the multiline input field.
+ */
+export interface FieldMultilineInputFromJsonConfig extends
+    FieldMultilineInputConfig {
+  text?: string;
+}
diff --git a/core/field_number.ts b/core/field_number.ts
index dd0938782..0285b2a15 100644
--- a/core/field_number.ts
+++ b/core/field_number.ts
@@ -17,7 +17,7 @@ goog.declareModuleId('Blockly.FieldNumber');
 
 import {Field} from './field.js';
 import * as fieldRegistry from './field_registry.js';
-import {FieldTextInput} from './field_textinput.js';
+import {FieldTextInputConfig, FieldTextInput} from './field_textinput.js';
 import * as aria from './utils/aria.js';
 import type {Sentinel} from './utils/sentinel.js';
 
@@ -70,7 +70,7 @@ export class FieldNumber extends FieldTextInput {
   constructor(
       opt_value?: string|number|Sentinel, opt_min?: string|number|null,
       opt_max?: string|number|null, opt_precision?: string|number|null,
-      opt_validator?: Function|null, opt_config?: AnyDuringMigration) {
+      opt_validator?: Function|null, opt_config?: FieldNumberConfig) {
     // Pass SENTINEL so that we can define properties before value validation.
     super(Field.SKIP_SETUP);
 
@@ -92,11 +92,11 @@ export class FieldNumber extends FieldTextInput {
    * Configure the field based on the given map of options.
    * @param config A map of options to configure the field based on.
    */
-  override configure_(config: AnyDuringMigration) {
+  protected override configure_(config: FieldNumberConfig) {
     super.configure_(config);
-    this.setMinInternal_(config['min']);
-    this.setMaxInternal_(config['max']);
-    this.setPrecisionInternal_(config['precision']);
+    this.setMinInternal_(config.min);
+    this.setMaxInternal_(config.max);
+    this.setPrecisionInternal_(config.precision);
   }
 
   /**
@@ -298,14 +298,30 @@ export class FieldNumber extends FieldTextInput {
    * @nocollapse
    * @internal
    */
-  static override fromJson(options: AnyDuringMigration): FieldNumber {
+  static override fromJson(options: FieldNumberFromJsonConfig): FieldNumber {
     // `this` might be a subclass of FieldNumber if that class doesn't override
     // the static fromJson method.
     return new this(
-        options['value'], undefined, undefined, undefined, undefined, options);
+        options.value, undefined, undefined, undefined, undefined, options);
   }
 }
 
 fieldRegistry.register('field_number', FieldNumber);
 
 (FieldNumber.prototype as AnyDuringMigration).DEFAULT_VALUE = 0;
+
+/**
+ * Config options for the number field.
+ */
+export interface FieldNumberConfig extends FieldTextInputConfig {
+  min?: number;
+  max?: number;
+  precision?: number;
+}
+
+/**
+ * fromJson config options for the number field.
+ */
+export interface FieldNumberFromJsonConfig extends FieldNumberConfig {
+  value?: number;
+}
diff --git a/core/field_textinput.ts b/core/field_textinput.ts
index f154485a8..ed36b6eba 100644
--- a/core/field_textinput.ts
+++ b/core/field_textinput.ts
@@ -23,7 +23,7 @@ import * as browserEvents from './browser_events.js';
 import * as dialog from './dialog.js';
 import * as dropDownDiv from './dropdowndiv.js';
 import * as eventUtils from './events/utils.js';
-import {Field} from './field.js';
+import {FieldConfig, Field} from './field.js';
 import * as fieldRegistry from './field_registry.js';
 import {Msg} from './msg.js';
 import * as aria from './utils/aria.js';
@@ -105,7 +105,7 @@ export class FieldTextInput extends Field {
    */
   constructor(
       opt_value?: string|Sentinel, opt_validator?: Function|null,
-      opt_config?: AnyDuringMigration) {
+      opt_config?: FieldTextInputConfig) {
     super(Field.SKIP_SETUP);
 
     if (opt_value === Field.SKIP_SETUP) {
@@ -120,10 +120,10 @@ export class FieldTextInput extends Field {
     }
   }
 
-  override configure_(config: AnyDuringMigration) {
+  protected override configure_(config: FieldTextInputConfig) {
     super.configure_(config);
-    if (typeof config['spellcheck'] === 'boolean') {
-      this.spellcheck_ = config['spellcheck'];
+    if (config.spellcheck !== undefined) {
+      this.spellcheck_ = config.spellcheck;
     }
   }
 
@@ -564,8 +564,8 @@ export class FieldTextInput extends Field {
    * @nocollapse
    * @internal
    */
-  static fromJson(options: AnyDuringMigration): FieldTextInput {
-    const text = parsing.replaceMessageReferences(options['text']);
+  static fromJson(options: FieldTextInputFromJsonConfig): FieldTextInput {
+    const text = parsing.replaceMessageReferences(options.text);
     // `this` might be a subclass of FieldTextInput if that class doesn't
     // override the static fromJson method.
     return new this(text, undefined, options);
@@ -575,3 +575,17 @@ export class FieldTextInput extends Field {
 fieldRegistry.register('field_input', FieldTextInput);
 
 (FieldTextInput.prototype as AnyDuringMigration).DEFAULT_VALUE = '';
+
+/**
+ * Config options for the text input field.
+ */
+export interface FieldTextInputConfig extends FieldConfig {
+  spellcheck?: boolean;
+}
+
+/**
+ * fromJson config options for the text input field.
+ */
+export interface FieldTextInputFromJsonConfig extends FieldTextInputConfig {
+  text?: string;
+}
diff --git a/core/field_variable.ts b/core/field_variable.ts
index 39fe3f3ba..bd118ef3e 100644
--- a/core/field_variable.ts
+++ b/core/field_variable.ts
@@ -19,7 +19,7 @@ goog.declareModuleId('Blockly.FieldVariable');
 import './events/events_block_change.js';
 
 import type {Block} from './block.js';
-import {Field} from './field.js';
+import {Field, FieldConfig} from './field.js';
 import {FieldDropdown} from './field_dropdown.js';
 import * as fieldRegistry from './field_registry.js';
 import * as internalConstants from './internal_constants.js';
@@ -84,7 +84,7 @@ export class FieldVariable extends FieldDropdown {
   constructor(
       varName: string|null|Sentinel, opt_validator?: Function,
       opt_variableTypes?: string[], opt_defaultType?: string,
-      opt_config?: AnyDuringMigration) {
+      opt_config?: FieldVariableConfig) {
     super(Field.SKIP_SETUP);
 
     /**
@@ -123,9 +123,9 @@ export class FieldVariable extends FieldDropdown {
    * Configure the field based on the given map of options.
    * @param config A map of options to configure the field based on.
    */
-  protected override configure_(config: AnyDuringMigration) {
+  protected override configure_(config: FieldVariableConfig) {
     super.configure_(config);
-    this.setTypes_(config['variableTypes'], config['defaultType']);
+    this.setTypes_(config.variableTypes, config.defaultType);
   }
 
   /**
@@ -475,8 +475,9 @@ export class FieldVariable extends FieldDropdown {
    * @nocollapse
    * @internal
    */
-  static override fromJson(options: AnyDuringMigration): FieldVariable {
-    const varName = parsing.replaceMessageReferences(options['variable']);
+  static override fromJson(options: FieldVariableFromJsonConfig):
+      FieldVariable {
+    const varName = parsing.replaceMessageReferences(options.variable);
     // `this` might be a subclass of FieldVariable if that class doesn't
     // override the static fromJson method.
     return new this(varName, undefined, undefined, undefined, options);
@@ -527,3 +528,18 @@ export class FieldVariable extends FieldDropdown {
 }
 
 fieldRegistry.register('field_variable', FieldVariable);
+
+/**
+ * Config options for the variable field.
+ */
+export interface FieldVariableConfig extends FieldConfig {
+  variableTypes?: string[];
+  defaultType?: string;
+}
+
+/**
+ * fromJson config options for the variable field.
+ */
+export interface FieldVariableFromJsonConfig extends FieldVariableConfig {
+  variable?: string;
+}
diff --git a/tests/mocha/field_image_test.js b/tests/mocha/field_image_test.js
index 62826398a..4a20a790f 100644
--- a/tests/mocha/field_image_test.js
+++ b/tests/mocha/field_image_test.js
@@ -22,7 +22,6 @@ suite('Image Fields', function() {
    * @type {!Array<!FieldCreationTestCase>}
    */
   const invalidValueTestCases = [
-    {title: 'Undefined Src', value: undefined, args: [undefined, 1, 1]},
     {title: 'Undefined Size', value: 'src', args: ['src', undefined, undefined]},
     {title: 'Zero Size', value: 'src', args: ['src', 0, 0]},
     {title: 'Non-Parsable String for Size', value: 'src', args: ['src', 'bad', 'bad']},