parseSchema

Turns a tool's inputSchema into a SchemaNode object.

Turns a tool’s inputSchema into a SchemaNode object. Chrome returns inputSchema as a JSON string and the polyfill returns an object, so the devtools read both through this; use it when you build a UI from getTools().

Import

import { parseSchema } from "@webmcp-agents/devtools";
import type { SchemaNode } from "@webmcp-agents/devtools";

Example

List each tool’s parameters, whichever shape the browser gave.

import { parseSchema } from "@webmcp-agents/devtools";

// Chrome returns each inputSchema as a JSON string, the polyfill as
// an object: parseSchema reads both.
const tools = await document.modelContext?.getTools();

for (const tool of tools ?? []) {
  const schema = parseSchema(tool.inputSchema);
  console.log(tool.name, Object.keys(schema.properties ?? {}));
}

Options

parseSchema(schema) takes one argument.

Name	Type	Default	Description
`schema`	`ModelContextToolInfo["inputSchema"]`	required	The schema from `document.modelContext.getTools()`: a JSON string (Chrome) or an object (polyfill).

`SchemaNode`

The slice of JSON Schema the runner understands. Unknown keywords pass through the index signature.

Name	Type	Description
`type`	`string \| string[]`	The JSON Schema type; `["string", "null"]` reads as `"string"`.
`title`	`string`	The label `SchemaForm` shows instead of the property name.
`description`	`string`	The parameter’s description; `defaultValueFor` takes a sample from `e.g. …` in it.
`default`	`unknown`	The starting value in the form.
`enum`	`unknown[]`	Allowed values, shown as a select.
`const`	`unknown`	A fixed value.
`format`	`string`	`date`, `email`, `uri`: the form’s input type and sample value.
`minimum`	`number`	Lower bound of a number, and its starting value.
`maximum`	`number`	Upper bound of a number.
`maxLength`	`number`	A string longer than 120 gets a textarea.
`properties`	`Record<string, SchemaNode>`	An object’s parameters.
`required`	`string[]`	Names of the required properties.
`items`	`SchemaNode`	The schema of an array’s items.

Returns

A SchemaNode. An object is returned as is; undefined gives {}. A string is parsed; a string that is not JSON, or does not parse to an object, gives {}.

Notes

A broken schema reads as empty rather than throwing.
WebMCP input schemas are shallow (a form’s fields, a tool’s zod object), so SchemaNode stays small. Anything else falls back to raw JSON in SchemaForm.
ToolView.schema in the store is already parsed with this.