How do I install the Using MCP Tools skill?

Run npx skillmds@latest add letta-ai/using-mcp-tools in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Using MCP Tools safe to use?

This skill has not completed SkillMD's automated safety review yet. Capability flags: docs only. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Using MCP Tools?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Using MCP Tools free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Using MCP Tools?

letta-ai (@letta-ai) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Using MCP Tools by letta-ai — Agent Skill

Name: Using MCP Tools
Rating: 4.2 (5 reviews)
Author: letta-ai

Using MCP Tools

Reference for the `letta mcp` CLI, which finds and invokes MCP tools available to this agent. A system reminder already lists your connected MCP servers and the basic search/schema/call commands; invoke this skill when you need more — browsing a server's tools, passing large or file-based arguments, tuning search, or troubleshooting missing servers, tools, and errors.

letta-ai 03b8d4c 3.5 KB Updated Sep 10, 2026

File contents

Using MCP tools

letta mcp gives the agent one unified view of every MCP server it can reach: servers connected to the agent in Letta Cloud and servers configured locally on this machine. It works from any surface where the agent runs — cloud sandboxes (chat.letta.com), Letta Desktop, and terminals. All output is JSON.

Commands

letta mcp list                                # servers: [{name, transport}]
letta mcp get <server>                        # one server's connection configuration (credentials redacted)
letta mcp tools [server]                      # tool names + descriptions only
letta mcp tools [server] --full               # ...including every tool's complete schema
letta mcp schema <tool-name>                  # one tool's complete schema
letta mcp search <query> [--mode] [--limit]   # ranked tool schemas: [{tool, rank, score}]
letta mcp call <tool-name> [--args | --args-file]  # run a tool, print a CallToolResult

Every command accepts --agent <id>, defaulting to LETTA_AGENT_ID/AGENT_ID — do not pass it unless targeting another agent.

Search options

--mode <hybrid|vector|fts> — default hybrid. vector uses server-side embeddings and covers only cloud-connected servers; fts and hybrid also rank local tools lexically. Agents on a local backend cannot use vector.
--limit <n> — result count, 1-100 (default 5).
Rank order is meaningful; absolute scores are not comparable across queries. When even the top results look unrelated to the query, no relevant tool likely exists — do not force the best-ranked one.

Call arguments and results

--args '<json>' — inline JSON object.
--args-file <path> — read the JSON object from a file; --args-file - reads stdin. Use these for large or shell-quoting-hostile payloads.
Output is an MCP CallToolResult: content (array of typed blocks), optional structuredContent, and isError.
Exit codes: 0 success, 1 CLI/usage error (JSON on stderr: {error: {code, message, hint?}}), 2 the tool ran and returned an error result — read content for the server's message, fix the arguments, and retry.
Summarize relevant results instead of pasting large raw payloads.

Troubleshooting

list empty → no MCP servers are available. Ask the user to connect one on the Letta Cloud MCP servers page or configure a local one in the Letta Code app.
Cloud server with no tools (or 0 tools in the reminder) → tools were never synced. Ask the user to resync it from the MCP servers page; the CLI has no refresh action.
unauthorized or another auth error on call → the server's stored credentials are missing or stale (tools can still list from previously synced rows). Ask the user to re-authenticate the server: cloud servers on the MCP servers page, local OAuth servers by connecting once in the Letta Code app — this CLI is non-interactive and only reuses persisted credentials.
ambiguous_server_name → two servers share a name; the error hint explains how to disambiguate.
Duplicate tool names across servers get a numeric suffix (_2); the printed name is always the callable one.

---name: using-mcp-toolsdescription: Reference for the `letta mcp` CLI, which finds and invokes MCP tools available to this agent. A system reminder already lists your connected MCP servers and the basic search/schema/call commands; invoke this skill when you need more — browsing a server's tools, passing large or file-based arguments, tuning search, or troubleshooting missing servers, tools, and errors.---# Using MCP tools`letta mcp` gives the agent one unified view of every MCP server it can reach: servers connected to the agent in Letta Cloud and servers configured locally on this machine. It works from any surface where the agent runs — cloud sandboxes (chat.letta.com), Letta Desktop, and terminals. All output is JSON.## Commands```bashletta mcp list # servers: [{name, transport}]letta mcp get <server> # one server's connection configuration (credentials redacted)letta mcp tools [server] # tool names + descriptions onlyletta mcp tools [server] --full # ...including every tool's complete schemaletta mcp schema <tool-name> # one tool's complete schemaletta mcp search <query> [--mode] [--limit] # ranked tool schemas: [{tool, rank, score}]letta mcp call <tool-name> [--args | --args-file] # run a tool, print a CallToolResult```Every command accepts `--agent <id>`, defaulting to `LETTA_AGENT_ID`/`AGENT_ID` — do not pass it unless targeting another agent.## Search options- `--mode <hybrid|vector|fts>` — default `hybrid`. `vector` uses server-side embeddings and covers only cloud-connected servers; `fts` and `hybrid` also rank local tools lexically. Agents on a local backend cannot use `vector`.- `--limit <n>` — result count, 1-100 (default 5).- Rank order is meaningful; absolute scores are not comparable across queries. When even the top results look unrelated to the query, no relevant tool likely exists — do not force the best-ranked one.## Call arguments and results- `--args '<json>'` — inline JSON object.- `--args-file <path>` — read the JSON object from a file; `--args-file -` reads stdin. Use these for large or shell-quoting-hostile payloads.- Output is an MCP CallToolResult: `content` (array of typed blocks), optional `structuredContent`, and `isError`.- Exit codes: `0` success, `1` CLI/usage error (JSON on stderr: `{error: {code, message, hint?}}`), `2` the tool ran and returned an error result — read `content` for the server's message, fix the arguments, and retry.- Summarize relevant results instead of pasting large raw payloads.## Troubleshooting- `list` empty → no MCP servers are available. Ask the user to connect one on the Letta Cloud MCP servers page or configure a local one in the Letta Code app.- Cloud server with no tools (or `0 tools` in the reminder) → tools were never synced. Ask the user to resync it from the MCP servers page; the CLI has no refresh action.- `unauthorized` or another auth error on `call` → the server's stored credentials are missing or stale (`tools` can still list from previously synced rows). Ask the user to re-authenticate the server: cloud servers on the MCP servers page, local OAuth servers by connecting once in the Letta Code app — this CLI is non-interactive and only reuses persisted credentials.- `ambiguous_server_name` → two servers share a name; the error hint explains how to disambiguate.- Duplicate tool names across servers get a numeric suffix (`_2`); the printed name is always the callable one.

Frequently asked questions