MCPTool.ts

tools/MCPTool/MCPTool.ts

tool-system mcp

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2170

Bytes

Exports

Imports

Keywords

What this is

This page documents one file from the repository and includes its full source so you can read it without leaving the docs site.

Beginner explanation

This file is part of the tool layer, which means it describes actions the system can perform for the user or model.

How it is used

Start from the exports list and related files. Those are the easiest clues for where this file fits into the system.

Expert explanation

Architecturally, this file intersects with tool-system, mcp. It contains 78 lines, 8 detected imports, and 4 detected exports.

Important relationships

Detected exports

inputSchema
outputSchema
Output
MCPTool

Keywords

inputschemaoutputschemaoverriddenmcpclientoutputlazyschemaprompttoolutilspermissionresult

Detected imports

zod/v4
../../Tool.js
../../utils/lazySchema.js
../../utils/permissions/PermissionResult.js
../../utils/terminal.js
./prompt.js
./UI.js
../../types/tools.js

Source notes

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Full source

import { z } from 'zod/v4'
import { buildTool, type ToolDef } from '../../Tool.js'
import { lazySchema } from '../../utils/lazySchema.js'
import type { PermissionResult } from '../../utils/permissions/PermissionResult.js'
import { isOutputLineTruncated } from '../../utils/terminal.js'
import { DESCRIPTION, PROMPT } from './prompt.js'
import {
  renderToolResultMessage,
  renderToolUseMessage,
  renderToolUseProgressMessage,
} from './UI.js'

// Allow any input object since MCP tools define their own schemas
export const inputSchema = lazySchema(() => z.object({}).passthrough())
type InputSchema = ReturnType<typeof inputSchema>

export const outputSchema = lazySchema(() =>
  z.string().describe('MCP tool execution result'),
)
type OutputSchema = ReturnType<typeof outputSchema>

export type Output = z.infer<OutputSchema>

// Re-export MCPProgress from centralized types to break import cycles
export type { MCPProgress } from '../../types/tools.js'

export const MCPTool = buildTool({
  isMcp: true,
  // Overridden in mcpClient.ts with the real MCP tool name + args
  isOpenWorld() {
    return false
  },
  // Overridden in mcpClient.ts
  name: 'mcp',
  maxResultSizeChars: 100_000,
  // Overridden in mcpClient.ts
  async description() {
    return DESCRIPTION
  },
  // Overridden in mcpClient.ts
  async prompt() {
    return PROMPT
  },
  get inputSchema(): InputSchema {
    return inputSchema()
  },
  get outputSchema(): OutputSchema {
    return outputSchema()
  },
  // Overridden in mcpClient.ts
  async call() {
    return {
      data: '',
    }
  },
  async checkPermissions(): Promise<PermissionResult> {
    return {
      behavior: 'passthrough',
      message: 'MCPTool requires permission.',
    }
  },
  renderToolUseMessage,
  // Overridden in mcpClient.ts
  userFacingName: () => 'mcp',
  renderToolUseProgressMessage,
  renderToolResultMessage,
  isResultTruncated(output: Output): boolean {
    return isOutputLineTruncated(output)
  },
  mapToolResultToToolResultBlockParam(content, toolUseID) {
    return {
      tool_use_id: toolUseID,
      type: 'tool_result',
      content,
    }
  },
} satisfies ToolDef<InputSchema, Output>)