mcp-toolsmith 0.4.0

Audit and compile Python tool schemas for LLM agents before your agent uses them.

mcp-toolsmith

mcp-toolsmith audits and compiles Python tool schemas for LLM agents, catching vague names, missing argument descriptions, oversized schemas, overlapping tools, and prompt-injection-like metadata before your agent uses them.

Pre-1.0: JSON tool files and static Python audits are safe by default. Python execution requires --execute and should only be used with trusted code. The public API may change before 1.0.0.

Tool schemas are not just documentation. In MCP, OpenAI-style tool calling, and agent frameworks, names, descriptions, and input schemas shape whether the model chooses the right tool and fills arguments correctly.

Install

pip install mcp-toolsmith

For local development:

python -m pip install -e ".[dev]"

Why?

LLM agents often fail because tool metadata is ambiguous.

Bad tool:

def run(query: str):
    """Run operation."""
    return query

Audit:

mcp-toolsmith audit tools.py --execute --all-public --fail-on warning

Output:

WARNING name.vague: Tool name is too generic for reliable tool selection.
WARNING description.too_short: Tool description is too short to guide model selection.
WARNING schema.arg_description_missing: Argument descriptions are missing for: query.

Usage

Audit JSON tool definitions

JSON tool definitions are safe by default:

mcp-toolsmith audit tools.json

Example JSON input:

{
  "tools": [
    {
      "name": "search_docs",
      "description": "Search project documentation by natural language query.",
      "inputSchema": {
        "type": "object",
        "properties": {
          "query": {
            "type": "string",
            "description": "Question or topic to search for."
          },
          "limit": {
            "type": "integer",
            "description": "Maximum number of results to return.",
            "default": 5
          }
        },
        "required": ["query"]
      }
    }
  ]
}

Example audit output:

OK Audited 1 tool(s) from tools.json
Mode: json
Profile: generic
Errors: 0  Warnings: 0

search_docs [mcp] ~55 schema tokens
  No findings

Compile tools

Compile to MCP-style tool definitions:

mcp-toolsmith compile tools.json --target mcp

Compile to OpenAI-style function definitions:

mcp-toolsmith compile tools.json --target openai

Audit trusted Python files

Python files are parsed statically by default:

mcp-toolsmith audit tools.py

This discovers @tool-decorated functions without executing the file:

from mcp_toolsmith import tool


@tool
def search_docs(query: str, limit: int = 5) -> list[str]:
    """Search project documentation by natural language query.

    Args:
        query: Question or topic to search for.
        limit: Maximum number of results to return.
    """
    return []

Static mode maps common annotations such as str, int, float, bool, dict, and list[str]. Use runtime execution only for trusted files when you need full Pydantic/runtime schema generation:

mcp-toolsmith audit tools.py --execute
mcp-toolsmith compile tools.py --target mcp --execute

Use --execute only for trusted files. In both static and execution modes, default Python discovery only includes functions decorated with @tool.

Use decorator arguments to override the generated tool name or description:

from mcp_toolsmith import tool


@tool(
    name="search_project_docs",
    description="Search project docs and return matching document IDs.",
)
def search_docs(query: str, limit: int = 5) -> list[str]:
    """Search project documentation by natural language query."""
    return []

Use --all-public to include every public top-level function and Pydantic model:

mcp-toolsmith audit tools.py --execute --all-public
mcp-toolsmith compile tools.py --target mcp --execute --all-public

--all-public is mainly a compatibility path for early alpha behavior. For new Python tool files, prefer @tool.

Use --fail-on to tune CI behavior:

mcp-toolsmith audit tools.py --fail-on error
mcp-toolsmith audit tools.py --fail-on warning
mcp-toolsmith audit tools.py --fail-on never

The default is error.

Provider compatibility profiles

Audit a tool schema for OpenAI-style tool calling:

mcp-toolsmith audit tools.py --profile openai

Audit a tool schema for MCP compatibility:

mcp-toolsmith audit tools.py --profile mcp

Use this in CI:

mcp-toolsmith audit tools.py --profile openai --fail-on warning

The default profile is generic, which keeps the provider-neutral audit behavior from earlier releases.

More copy-pasteable examples live in examples.

Python API

from mcp_toolsmith import audit_file, compile_file

report = audit_file("tools.json")
openai_report = audit_file("tools.json", profile="openai")
report.print()
openai_report.print()

mcp_tools = compile_file("tools.json", target="mcp")
openai_tools = compile_file("tools.json", target="openai")

For trusted Python files:

report = audit_file("tools.py")
report = audit_file("tools.py", execute=True)
mcp_tools = compile_file("tools.py", target="mcp", execute=True)

To opt into broad Python discovery:

report = audit_file("tools.py", execute=True, all_public=True)
mcp_tools = compile_file("tools.py", target="mcp", execute=True, all_public=True)

Checks

Check	Why it matters
Vague tool names	Agents may pick the wrong tool when names are generic
Missing descriptions	Tool selection depends heavily on clear descriptions
Missing argument descriptions	Models need argument-level context
Oversized schemas	Large schemas cost tokens and can distract smaller models
Overlapping tools	Similar tools make tool choice unstable
Tool-poisoning language	Tool metadata is part of the prompt surface

Roadmap

Version	Goal
0.2.0	Decorator-based Python tool discovery
0.3.0	Safe static audit for @tool-decorated Python functions
0.4.0	Provider compatibility profiles for OpenAI and MCP tool schemas
0.5.0	Deterministic schema compaction and rewriting
1.0.0	Stable public API and compatibility matrix

License

MIT