mcp-cli

mcp-cli

A single-binary MCP client for the shell. It calls one tool on one MCP server and prints the bare payload — no envelope, no session juggling, no hand-built JSON-RPC.

Servers are not configured twice: mcp-cli reads the same configuration Claude Code uses, so anything in claude mcp list is callable from a script.

echo '{"libraryName": "Go", "query": "http server"}' | mcp-cli context7 resolve-library-id

Install

go install github.com/tkukushkin/mcp-cli@latest

Or grab a prebuilt binary for darwin, linux or windows on amd64/arm64 from the releases page.

To teach Claude Code about the binary, install the skill it carries:

mcp-cli install-skill

It writes ~/.claude/skills/mcp-cli/, so the instructions Claude reads always match the installed version — rerun it after an upgrade. The directory ignores itself in git.

Usage

mcp-cli <server> <tool>

• <server> — the name as it appears in claude mcp list.
• <tool> — the bare tool name, without the mcp__<server>__ prefix.
• Arguments are a JSON object on stdin. For a tool that takes none, use < /dev/null — or just run it interactively, since a TTY stdin also means {}.
• stdout is the tool's payload: structuredContent as compact JSON when the server provides it, otherwise the text content as-is (which may itself be JSON).
• Exit code is 0 on success, 1 on failure, with the error text on stderr (server not found, connection failure, or the tool's own error message).

Configuration

No config file of its own. Servers are looked up by name, first match wins, in the working directory and then in each directory above it:

1. ~/.claude.json — projects["<dir>"].mcpServers (local scope)
2. <dir>/.mcp.json — mcpServers (project scope)
3. ~/.claude.json — mcpServers (user scope)

${VAR} and ${VAR:-default} in a config value are expanded from the environment, as Claude Code expands them.

OAuth

Servers behind claude mcp login work: mcp-cli shares OAuth credentials with Claude Code, refreshing them in place when they expire.

Scope

tools/call only, deliberately. Discovery (tools/list, resources, prompts) is what an MCP host is for; this is the escape hatch for when you're not in one.

License

MIT