Schema Modifiers

Schema modifiers are part of Composio SDK’s powerful middleware capabilities that allow you to customize and extend the behavior of tools.

Schema Modifiers

Schema modifiers transform a tool’s schema before the tool is seen by an agent.

Useful for:

• Modifying or rewriting the tool description to better fit your use case.
• Adding arguments to the tool. For example, adding a thought argument to the tool to prompt the agent to explain the reasoning.
• Hiding arguments from the tool. In cases where the argument is irrelevant to the tool.
• Adding extra arguments to the tool schema for custom use cases or execution.
• Adding default values to tool arguments.

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from composio import Composio, schema_modifier
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from composio.types import Tool
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user_id = "your@email.com"
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@schema_modifier(tools=["HACKERNEWS_GET_LATEST_POSTS"])
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def modify_schema(
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    tool: str,
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    toolkit: str,
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    schema: Tool,
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) -> Tool:
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    _ = schema.input_parameters["properties"].pop("page", None)
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    schema.input_parameters["required"] = ["size"]
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    return schema
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tools = composio.tools.get(
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    user_id=user_id,
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    tools=["HACKERNEWS_GET_LATEST_POSTS", "HACKERNEWS_GET_USER"],
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    modifiers=[
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        modify_schema,
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    ]
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)

In using the above modified tool schema, the page argument is removed and the size argument is required.

You can test this out by viewing the tool call response in the LLM too!

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from openai import OpenAI
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from composio import Composio, schema_modifier
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from composio.types import Tool
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from composio_openai import OpenAIProvider
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@schema_modifier(tools=["HACKERNEWS_GET_LATEST_POSTS"])
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def modify_schema(
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    tool: str,
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    toolkit: str,
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    schema: Tool,
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) -> Tool:
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    _ = schema.input_parameters["properties"].pop("page", None)
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    schema.input_parameters["required"] = ["size"]
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    return schema
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# Initialize tools.
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openai_client = OpenAI()
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composio = Composio(provider=OpenAIProvider())
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# Define task.
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task = "Get the latest posts from Hacker News"
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# Get GitHub tools that are pre-configured
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tools = composio.tools.get(
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  user_id="default",
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  tools=['HACKERNEWS_GET_LATEST_POSTS', 'HACKERNEWS_GET_USER'],
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  modifiers=[
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      modify_schema,
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  ],
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)
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# Get response from the LLM
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response = openai_client.chat.completions.create(
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    model="gpt-4o-mini",
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    tools=tools,
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    messages=[
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        {"role": "system", "content": "You are a helpful assistant."},
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        {"role": "user", "content": task},
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    ],
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)
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print(response)
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# Execute the function calls.
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result = composio.provider.handle_tool_calls(response=response, user_id="default")
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print(result)

Example: Modifying the tool description

Sometimes you need to provide additional context to help the agent understand how to use a tool correctly. This example demonstrates modifying the description of the GITHUB_LIST_REPOSITORY_ISSUES tool to specify a default repository when none is provided.

In this example:

• We append additional instructions to the tool’s description
• The modified description tells the agent to use composiohq/composio as the default repository
• This helps prevent errors when the agent forgets to specify a repository parameter

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from composio import Composio, schema_modifier
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from composio.types import Tool
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from composio_google import GoogleProvider
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from google import genai
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from google.genai import types
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from uuid import uuid4
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composio = Composio(provider=GoogleProvider())
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client = genai.Client()
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user_id = uuid4()   # User ID from DB/App
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@schema_modifier(tools=["GITHUB_LIST_REPOSITORY_ISSUES"])
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def append_repository(
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    tool: str, 
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    toolkit: str,
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    schema: Tool,
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) -> Tool:
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    schema.description += " When not specified, use the `composiohq/composio` repository"
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    return schema
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tools = composio.tools.get(
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    user_id=user_id, tools=["GITHUB_LIST_REPOSITORY_ISSUES"], modifiers=[append_repository]
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)
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print(tools)