ToolCallFilter

The ToolCallFilter is an input processor that filters out tool calls and their results from the message history before sending to the model. This is useful when you want to exclude specific tool interactions from context or remove all tool calls entirely.

Usage example

import { ToolCallFilter } from "@mastra/core/processors";

// Exclude all tool calls
const filterAll = new ToolCallFilter();

// Exclude specific tools by name
const filterSpecific = new ToolCallFilter({
  exclude: ["searchDatabase", "sendEmail"],
});

Constructor parameters

options?:

Options

Configuration options for the tool call filter

Options

exclude?:

string[]

List of specific tool names to exclude. If not provided or undefined, all tool calls are excluded

Returns

id:

string

Processor identifier set to 'tool-call-filter'

name:

string

Processor display name set to 'ToolCallFilter'

processInput:

(args: { messages: MastraDBMessage[]; messageList: MessageList; abort: (reason?: string) => never; requestContext?: RequestContext }) => Promise<MessageList | MastraDBMessage[]>

Processes input messages to filter out tool calls and their results based on configuration

Extended usage example

src/mastra/agents/filtered-agent.ts

import { Agent } from "@mastra/core/agent";
import { ToolCallFilter } from "@mastra/core/processors";

export const agent = new Agent({
  name: "filtered-agent",
  instructions: "You are a helpful assistant",
  model: "openai:gpt-4o",
  tools: {
    searchDatabase,
    sendEmail,
    getWeather,
  },
  inputProcessors: [
    // Filter out database search tool calls from context
    // to reduce token usage while keeping other tool interactions
    new ToolCallFilter({
      exclude: ["searchDatabase"],
    }),
  ],
});

Filtering all tool calls

import { Agent } from "@mastra/core/agent";
import { ToolCallFilter } from "@mastra/core/processors";

export const agent = new Agent({
  name: "no-tools-context-agent",
  instructions: "You are a helpful assistant",
  model: "openai:gpt-4o",
  tools: {
    searchDatabase,
    sendEmail,
  },
  inputProcessors: [
    // Remove all tool calls from the message history
    // The agent can still use tools, but previous tool interactions
    // won't be included in the context
    new ToolCallFilter(),
  ],
});

Related

• Guardrails