MCP server - Function Description too Long

[michnovka]

What happened?

I have issues with some MCP servers due to their long description:

2025-02-08T21:22:07.862Z error: [api/server/controllers/agents/client.js #sendCompletion] Unhandled error type 400 Invalid 'tools[8].function.description': string too long. Expected ... [truncated]
2025-02-08T21:22:07.863Z error: [handleAbortError] AI response error; aborting request: 400 Invalid 'tools[8].function.description': string too long. Expected a string with maximum l... [truncated]
2025-02-08T21:22:07.867Z debug: [AgentController] Request closed

The error message is misleading too:

As far as I understand the error is not from AI provider as the message says, but from the librechat itself.

This is the description the server uses:

mcp-gateway  | 2025-02-08T21:21:02.758Z [verbose]: SSE -> STDIO: {"method":"tools/list","jsonrpc":"2.0","id":2}
mcp-gateway  | 2025-02-08T21:21:02.759Z [verbose]: STDIO -> SSE: {"jsonrpc":"2.0","id":2,"result":{"tools":[{"name":"sequentialthinking","description":"A detailed tool for dynamic and reflective problem-solving through thoughts.\nThis tool helps analyze problems through a flexible thinking process that can adapt and evolve.\nEach thought can build on, question, or revise previous insights as understanding deepens.\n\nWhen to use this tool:\n- Breaking down complex problems into steps\n- Planning and design with room for revision\n- Analysis that might need course correction\n- Problems where the full scope might not be clear initially\n- Problems that require a multi-step solution\n- Tasks that need to maintain context over multiple steps\n- Situations where irrelevant information needs to be filtered out\n\nKey features:\n- You can adjust total_thoughts up or down as you progress\n- You can question or revise previous thoughts\n- You can add more thoughts even after reaching what seemed like the end\n- You can express uncertainty and explore alternative approaches\n- Not every thought needs to build linearly - you can branch or backtrack\n- Generates a solution hypothesis\n- Verifies the hypothesis based on the Chain of Thought steps\n- Repeats the process until satisfied\n- Provides a correct answer\n\nParameters explained:\n- thought: Your current thinking step, which can include:\n* Regular analytical steps\n* Revisions of previous thoughts\n* Questions about previous decisions\n* Realizations about needing more analysis\n* Changes in approach\n* Hypothesis generation\n* Hypothesis verification\n- next_thought_needed: True if you need more thinking, even if at what seemed like the end\n- thought_number: Current number in sequence (can go beyond initial total if needed)\n- total_thoughts: Current estimate of thoughts needed (can be adjusted up/down)\n- is_revision: A boolean indicating if this thought revises previous thinking\n- revises_thought: If is_revision is true, which thought number is being reconsidered\n- branch_from_thought: If branching, which thought number is the branching point\n- branch_id: Identifier for the current branch (if any)\n- needs_more_thoughts: If reaching end but realizing more thoughts needed\n\nYou should:\n1. Start with an initial estimate of needed thoughts, but be ready to adjust\n2. Feel free to question or revise previous thoughts\n3. Don't hesitate to add more thoughts if needed, even at the \"end\"\n4. Express uncertainty when present\n5. Mark thoughts that revise previous thinking or branch into new paths\n6. Ignore information that is irrelevant to the current step\n7. Generate a solution hypothesis when appropriate\n8. Verify the hypothesis based on the Chain of Thought steps\n9. Repeat the process until satisfied with the solution\n10. Provide a single, ideally correct answer as the final output\n11. Only set next_thought_needed to false when truly done and a satisfactory answer is reached","inputSchema":{"type":"object","properties":{"thought":{"type":"string","description":"Your current thinking step"},"nextThoughtNeeded":{"type":"boolean","description":"Whether another thought step is needed"},"thoughtNumber":{"type":"integer","description":"Current thought number","minimum":1},"totalThoughts":{"type":"integer","description":"Estimated total thoughts needed","minimum":1},"isRevision":{"type":"boolean","description":"Whether this revises previous thinking"},"revisesThought":{"type":"integer","description":"Which thought is being reconsidered","minimum":1},"branchFromThought":{"type":"integer","description":"Branching point thought number","minimum":1},"branchId":{"type":"string","description":"Branch identifier"},"needsMoreThoughts":{"type":"boolean","description":"If more thoughts are needed"}},"required":["thought","nextThoughtNeeded","thoughtNumber","totalThoughts"]}}]}}

Steps to Reproduce

1. use sequential-thinking MCP
2. enable with agent
3. try to use

What browsers are you seeing the problem on?

No response

Relevant log output

Screenshots

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[danny-avila]

The limitation comes upstream from the provider, which Provider are you using here?

[michnovka]

This is gpt4o.

[michnovka]

I have tried this with claude and gemini, same error.

How come this is a response from upstream,the error looks like it complains about JS code. Can the "AI Response code" be some bug due to improper catch where internal JS error is thrown as AI response error and thus interpreted like server error while in fact its issue with local code?

librechat-api          | 2025-02-11T21:50:19.509Z error: [api/server/controllers/agents/client.js #sendCompletion] Unhandled error type 400 Invalid 'tools[8].function.description': string too long. Expected ... [truncated]
librechat-api          | 2025-02-11T21:50:19.509Z error: [handleAbortError] AI response error; aborting request: 400 Invalid 'tools[8].function.description': string too long. Expected a string with maximum l... [truncated]