mcptokens

375 tokens in your agent's harness. One tool, inspect, that counts the tool-definition cost of any other MCP server (stdio or Streamable HTTP) before you enable it.

pip install mcptokens

Why

When your agent enables a new MCP server, its tools enter the agent's context on every turn. The cost compounds fast. mcptokens lets the agent ask is this server cheap enough? before flipping the switch.

Transports

Same tool, same response shape:

• stdio (default): spawn a local process and speak JSON-RPC on its stdin/stdout.
• streamable_http: POST initialize and tools/list to a remote MCP endpoint per MCP 2025-03-26. Server may reply via application/json (one message) or text/event-stream.

How

Add mcptokens to your agent's MCP config (Claude Code, Pi, OpenCode, Codex, ...). The agent gains one tool:

inspect(command=["python", "-m", "some_mcp_server"])
# stdio spawn argv, same as your MCP config

inspect(command=["hound"])
# pre-installed binary

inspect(
    transport="streamable_http",
    url="http://localhost:8080/mcp",
    headers={"Authorization": "Bearer ..."},  # optional
)
# remote MCP server

# Returns the same JSON shape every call:
# {ok, server, tool_count, wire_total_tokens,
#  tools: [{name, total}], encoding, elapsed_ms, version}

wire_total_tokens is the number to report. Use it BEFORE enabling a candidate server: a large value means don't enable.

The numbers

Install

pip install mcptokens

Add mcptokens to your agent's mcpServers / mcp_servers. Done.

CLI (debug surface)

mcptokens python -m some_mcp_server     # human table
mcptokens --json python -m some_mcp_server   # pipeline-friendly JSON
mcptokens --timeout 30 python -m srv    # custom spawn, custom timeout
mcptokens serve                         # run as an MCP server

License

MIT. pip install mcptokens from the canonical PyPI index.