gem-hunter
Language: Python
Turn any MCP, OpenAPI, or GraphQL server into a CLI — at runtime, with zero codegen
Turn any MCP server, OpenAPI spec, or GraphQL endpoint into a CLI — at runtime, with zero codegen.
Save 96–99% of the tokens wasted on tool schemas every turn.
Read the full writeup →
# Run directly without installing uvx mcp2cli --help # Or install globally uv tool install mcp2cli
mcp2cli ships with an installable skill that teaches AI coding agents (Claude Code, Cursor, Codex) how to use it. Once installed, your agent can discover and call any MCP server or OpenAPI endpoint — and even generate new skills from APIs.
npx skills add knowsuchagency/mcp2cli --skill mcp2cli
After installing, try prompts like:
mcp2cli --mcp https://mcp.example.com/sse — interact with an MCP servermcp2cli create a skill for https://api.example.com/openapi.json — generate a skill from an API# Connect to an MCP server over HTTP mcp2cli --mcp https://mcp.example.com/sse --list # Call a tool mcp2cli --mcp https://mcp.example.com/sse search --query "test" # With auth header mcp2cli --mcp https://mcp.example.com/sse --auth-header "x-api-key:sk-..." \ query --sql "SELECT 1" # Force a specific transport (skip streamable HTTP fallback dance) mcp2cli --mcp https://mcp.example.com/sse --transport sse --list # Search tools by name or description (case-insensitive substring match) mcp2cli --mcp https://mcp.example.com/sse --search "task"
--search implies --list and works across all modes (--mcp, --spec, --graphql, --mcp-stdio).
APIs that require OAuth are supported out of the box — across MCP, OpenAPI, and GraphQL modes. mcp2cli handles token acquisition, caching, and refresh automatically.
# Authorization code + PKCE flow (opens browser for login) mcp2cli --mcp https://mcp.example.com/sse --oauth --list mcp2cli --spec https://api.example.com/openapi.json --oauth --list mcp2cli --graphql https://api.example.com/graphql --oauth --list # Client credentials flow (machine-to-machine, no browser) mcp2cli --spec https://api.example.com/openapi.json \ --oauth-client-id "my-client-id" \ --oauth-client-secret "my-secret" \ list-pets # With specific scopes mcp2cli --graphql https://api.example.com/graphql --oauth --oauth-scope "read write" users # Local spec file — use --base-url for OAuth discovery mcp2cli --spec ./openapi.json --base-url https://api.example.com --oauth --list
Tokens are persisted in ~/.cache/mcp2cli/oauth/ so subsequent calls reuse existing tokens
and refresh automatically when they expire.
The default authorization-code flow starts a callback server on 127.0.0.1, which only
works when the browser runs on the same machine. On a VPS over SSH or in a container,
add --oauth-manual-callback: mcp2cli prints the authorization URL instead of opening a
browser, and reads the redirect back from stdin.
mcp2cli --mcp https://mcp.linear.app/mcp --oauth --oauth-manual-callback --list
Open the printed URL in a browser on any machine, authorize, then paste the URL you land
on. That page will fail to load — nothing is listening on the loopback port — which is
expected; only its address matters, because it carries the code and state parameters.
PKCE and state verification are unchanged, so paste the URL unmodified.
Sensitive values (--auth-header values, --oauth-client-id, --oauth-client-secret) support
env: and file: prefixes to avoid passing secrets as CLI arguments (which are visible in
process listings):
# Read from environment variable mcp2cli --mcp https://mcp.example.com/sse \ --auth-header "Authorization:env:MY_API_TOKEN" \ --list # Read from file mcp2cli --mcp https://mcp.example.com/sse \ --oauth-client-secret "file:/run/secrets/client_secret" \ --oauth-client-id "my-client-id" \ --list # Works with secret managers that inject env vars fnox exec -- mcp2cli --mcp https://mcp.example.com/sse \ --oauth-client-id "env:OAUTH_CLIENT_ID" \ --oauth-client-secret "env:OAUTH_CLIENT_SECRET" \ --list
# List tools from an MCP server mcp2cli --mcp-stdio "npx @modelcontextprotocol/server-filesystem /tmp" --list # Call a tool mcp2cli --mcp-stdio "npx @modelcontextprotocol/server-filesystem /tmp" \ read-file --path /tmp/hello.txt # Pass environment variables to the server process mcp2cli --mcp-stdio "node server.js" --env API_KEY=sk-... --env DEBUG=1 \ search --query "test"
Expose one or more filesystem roots when a server scopes operations to a
workspace. Paths are converted to file:// URIs; explicit roots must also use
the file:// scheme.
mcp2cli --mcp-stdio "npx @modelcontextprotocol/server-filesystem /tmp" \ --root "$PWD" --root file:///var/shared --list
Request prompt-argument or resource-template completions with
REF:ARG=PREFIX:
mcp2cli --mcp https://example.com/mcp \ --complete "greeting:name=San" mcp2cli --mcp https://example.com/mcp \ --complete "file:///docs/{topic}:topic=api"
Both options work when starting a persistent session; roots are retained by
the session daemon and completion requests can be sent through --session.
# List all commands from a remote spec mcp2cli --spec https://petstore3.swagger.io/api/v3/openapi.json --list # Call an endpoint mcp2cli --spec ./openapi.json --base-url https://api.example.com list-pets --status available # With auth mcp2cli --spec ./spec.json --auth-header "Authorization:Bearer tok_..." create-item --name "Test" # POST with JSON body from stdin echo '{"name": "Fido", "tag": "dog"}' | mcp2cli --spec ./spec.json create-pet --stdin # Flags given with --stdin are merged into the JSON (a conflicting value is an error) echo '{"name": "Fido"}' | mcp2cli --spec ./spec.json create-pet --tag dog --stdin # Local YAML spec mcp2cli --spec ./api.yaml --base-url http://localhost:8000 --list
# List all queries and mutations from a GraphQL endpoint mcp2cli --graphql https://api.example.com/graphql --list # Call a query mcp2cli --graphql https://api.example.com/graphql users --limit 10 # Call a mutation mcp2cli --graphql https://api.example.com/graphql create-user --name "Alice" --email "alice@example.com" # Override auto-generated selection set fields mcp2cli --graphql https://api.example.com/graphql --fields "id name email" users # With auth mcp2cli --graphql https://api.example.com/graphql --auth-header "Authorization:Bearer tok_..." users
mcp2cli introspects the endpoint, discovers queries and mutations, auto-generates selection sets, and constructs parameterized queries with proper variable declarations. No SDL parsing, no code generation — just point and run.
Tired of repeating --spec/--mcp/--mcp-stdio plus auth flags on every invocation? Bake them into a named configuration:
# Create a baked tool from an OpenAPI spec mcp2cli bake create petstore --spec https://api.example.com/spec.json \ --exclude "delete-*,update-*" --methods GET,POST --cache-ttl 7200 # Create a baked tool from an MCP stdio server mcp2cli bake create myfs --mcp-stdio "npx -y @modelcontextprotocol/server-filesystem /tmp" \ --include "search-*,list-*" --exclude "list-allowed-*" # Use a baked tool with @ prefix — no connection flags needed mcp2cli @petstore --list mcp2cli @petstore list-pets --limit 10 mcp2cli @myfs --list # search-files, list-directory, list-directory-with-sizes mcp2cli @myfs search-files --path /tmp --pattern "**/*.md" # pattern is a glob, relative to --path # Manage baked tools mcp2cli bake list # show all baked tools mcp2cli bake show petstore # show config (secrets masked) mcp2cli bake update petstore --cache-ttl 3600 mcp2cli bake remove petstore mcp2cli bake install petstore # creates ~/.local/bin/petstore wrapper mcp2cli bake install petstore --dir ./scripts/ # install wrapper to custom directory
Filtering options:
--include — comma-separated glob patterns to whitelist tools (e.g. "list-*,get-*")--exclude — comma-separated glob patterns to blacklist tools (e.g. "delete-*")--methods — comma-separated HTTP methods to allow (e.g. "GET,POST", OpenAPI only)Configs are stored in ~/.config/mcp2cli/baked.json. Override with MCP2CLI_CONFIG_DIR.
bake show masks the credential values it knows about — the OAuth client secret and every --auth-header value — while leaving env:/file: references readable so the config stays diagnosable. Values baked in with --env are printed as stored, so scrub those before pasting the output if an env var carries a token.
mcp2cli tracks tool invocations locally and uses that data to rank --list output, reducing token costs for LLM agents working with large servers.
# Default --list: ~1,400 tokens for 96 tools mcp2cli @myapi --list # Top 10 most-used tools, names only: ~20 tokens mcp2cli @myapi --list --top 10 --compact # Sort by most recently used mcp2cli @myapi --list --sort recent # Alphabetical sort mcp2cli @myapi --list --sort alpha
When usage data exists for a source, --list defaults to sorting by call frequency. Otherwise insertion order is preserved. Usage data is stored in ~/.cache/mcp2cli/usage.json.
--json forces valid JSON on stdout for every command, in every mode. It is the
machine-readable counterpart to the human-formatted default output, designed for LLM
agents and scripts that need to parse results reliably.
# --list emits a JSON array of command objects (name, description, parameters, ...) mcp2cli --mcp https://mcp.example.com/sse --list --json mcp2cli --spec ./openapi.json --list --json mcp2cli --graphql https://api.example.com/graphql --list --json # --list --json --compact emits a JSON array of names only mcp2cli --mcp https://mcp.example.com/sse --list --json --compact # MCP tool calls emit the FULL CallToolResult envelope — including # structuredContent and isError, not just the flattened text. This surfaces the # machine-readable result that modern MCP tools put in structuredContent. mcp2cli --mcp https://mcp.example.com/sse --json search --query "test" # { "content": [...], "structuredContent": {...}, "isError": false } # OpenAPI / GraphQL calls emit the response as JSON (non-JSON bodies become a JSON string) mcp2cli --spec ./openapi.json --json list-pets mcp2cli --graphql https://api.example.com/graphql --json users
--json takes precedence over --raw and --toon (both of which can produce
non-JSON), so it always wins — that is what makes it a reliable "force JSON" switch.
Indentation follows the usual rule: pretty on a TTY or with --pretty, compact when piped.
# Pretty-print JSON (also auto-enabled for TTY) mcp2cli --spec ./spec.json --pretty list-pets # Raw response body (no JSON parsing) mcp2cli --spec ./spec.json --raw get-data # Truncate large responses to first N records mcp2cli --spec ./spec.json --head 5 list-records # Pipe-friendly (compact JSON when not a TTY) mcp2cli --spec ./spec.json list-pets | jq '.[] | .name' # TOON output — token-efficient encoding for LLM consumption # Best for large uniform arrays (40-60% fewer tokens than JSON) mcp2cli --mcp https://mcp.example.com/sse --toon list-tags
Specs and MCP tool lists are cached in ~/.cache/mcp2cli/ with a 1-hour TTL by default.
# Force refresh mcp2cli --spec https://api.example.com/spec.json --refresh --list # Custom TTL (seconds) mcp2cli --spec https://api.example.com/spec.json --cache-ttl 86400 --list # Custom cache key mcp2cli --spec https://api.example.com/spec.json --cache-key my-api --list # Override cache directory MCP2CLI_CACHE_DIR=/tmp/my-cache mcp2cli --spec ./spec.json --list
Local file specs are never cached.
mcp2cli [global options] <subcommand> [command options]
Source (mutually exclusive, one required):
--spec URL|FILE OpenAPI spec (JSON or YAML, local or remote)
--mcp URL MCP server URL (HTTP/SSE)
--mcp-stdio CMD MCP server command (stdio transport)
--graphql URL GraphQL endpoint URL
Options:
--auth-header K:V HTTP header (repeatable, value supports env:/file: prefixes)
--base-url URL Override base URL from spec
--transport TYPE MCP HTTP transport: auto|sse|streamable (default: auto)
--env KEY=VALUE Env var for MCP stdio server (repeatable)
--root PATH|FILE_URI Expose a filesystem root to an MCP server (repeatable)
--complete SPEC Complete an MCP prompt or resource-template argument
--oauth Enable OAuth (authorization code + PKCE flow)
--oauth-client-id ID OAuth client ID (supports env:/file: prefixes)
--oauth-client-secret S OAuth client secret (supports env:/file: prefixes)
--oauth-scope SCOPE OAuth scope(s) to request
--oauth-manual-callback Print the auth URL and read the redirect from stdin
(for hosts with no reachable browser)
--cache-key KEY Custom cache key
--cache-ttl SECONDS Cache TTL (default: 3600)
--refresh Bypass cache
--list List available subcommands
--search PATTERN Search tools by name or description (implies --list)
--sort MODE Sort --list output: usage|recent|alpha|default
--top N Show only the top N tools in --list output
--compact Space-separated tool names only, no descriptions
--verbose Show full tool descriptions (unwrapped)
--fields FIELDS Override GraphQL selection set (e.g. "id name email")
--pretty Pretty-print JSON output
--raw Print raw response body
--json Force valid JSON output for every command (--list and tool
calls). MCP calls emit the full result envelope including
structuredContent. Takes precedence over --raw and --toon.
--toon Encode output as TOON (token-efficient for LLMs)
--head N Limit output to first N records (arrays)
--version Show version
Bake mode:
bake create NAME [opts] Save connection settings as a named tool
bake list List all baked tools
bake show NAME Show config (secrets masked)
bake update NAME [opts] Update a baked tool
bake remove NAME Delete a baked tool
bake install NAME Create ~/.local/bin wrapper script
@NAME [args] Run a baked tool (e.g. mcp2cli @petstore --list)
Subcommands and their flags are generated dynamically from the spec or MCP server tool definitions. Run <subcommand> --help for details.
For token savings analysis, architecture details, and comparison to Anthropic's Tool Search, see the full writeup on the OCAI blog.
# Install with test + MCP deps uv sync --extra test # Run tests uv run pytest tests/ -v # Run just the token savings tests uv run pytest tests/test_token_savings.py -v -s
mcp2cli works with both major versions of the MCP Python SDK (mcp>=1.26,<3),
so it never forces a resolver conflict with other tools in the same environment.
CI runs the suite against the declared floor, the latest 1.x, and the latest 2.x.
The two majors differ in ways that matter to a client — v2 renamed model fields
to snake_case, replaced streamablehttp_client, moved to httpx2, and dropped
the session-id element from the transport tuple. Those differences are confined
to a handful of helpers (_mcp_attr, _mcp_dump, _streamable_streams,
_list_tools_page, _resource_uri, _authorization_code_result); the rest of
the codebase is version-agnostic. The test fixtures speak the JSON-RPC wire
protocol directly and import no SDK, so they hold across majors.