Quick Reference: Tool Schema

Updated: 2026-05-26

Anthropic-Schema Tools

Tool	Name	Execution	Description
Bash	bash	Client	Run shell commands
Text Editor	text_editor	Client	Read, write, edit files
Computer Use	computer	Client	Control browser/desktop
Memory	memory	Client	Manage scratchpad memory
Web Search	web_search	Server	Search the web
Web Fetch	web_fetch	Server	Fetch URL content
Code Execution	code_execution	Server	Run Python code
Tool Search	tool_search	Server	Search available tools

User-Defined Tool Schema

{
  "name": "my_tool",
  "description": "What this tool does",
  "input_schema": {
    "type": "object",
    "properties": {
      "param1": {
        "type": "string",
        "description": "First parameter"
      },
      "param2": {
        "type": "integer",
        "description": "Second parameter"
      }
    },
    "required": ["param1"]
  }
}

Response Format

Tool Use Block (from Claude)

{
  "type": "tool_use",
  "id": "toolu_01ABC123",
  "name": "my_tool",
  "input": {
    "param1": "value",
    "param2": 42
  }
}

Tool Result Block (from your app)

{
  "type": "tool_result",
  "tool_use_id": "toolu_01ABC123",
  "content": "Result text or array"
}

Gotchas

Issue	Fix
Missing tool_use ID	Always extract id from the tool_use block
Wrong ID in result	tool_use_id must match exactly
Multiple tools	Claude can call several tools in one response
Error in tool	Return the error message as tool_result content
Long results	Large outputs count against context window