Function calling with deepseek-chat

[StefanRichterHuber]

What happened?

Version LibreChat v0.7.7

When trying to use function calling (specifically a custom MCP server) with deepseek-chat model, the first function call works, the model can call the tool and process the result. But each interaction afterwards breaks with an error.

Interaction is something like:
USER: Use tool
LLM: [LLM uses tool] here is the result.
USER: Great, summerize the result
LLM: [After ~30s of waiting] Something went wrong. Here's the specific error message we encountered: An error occurred while processing the request: 422 Failed to deserialize the JSON body into the target type: messages[6]: invalid type: sequence, expected a string at line 127 column 4`

Version Information

ghcr.io/danny-avila/librechat-dev latest 06e87a09ddf6 12 hours ago 945MB
ghcr.io/danny-avila/librechat-rag-api-dev-lite latest 49a785a50986 2 weeks ago 1.28GB

Steps to Reproduce

USER: Use tool
LLM: [LLM uses tool] here is the result.
USER: Great, summerize the result
LLM: [After ~30s of waiting] Something went wrong. Here's the specific error message we encountered: An error occurred while processing the request: 422 Failed to deserialize the JSON body into the target type: messages[6]: invalid type: sequence, expected a string at line 127 column 4`

What browsers are you seeing the problem on?

Firefox

Relevant log output

2025-04-29 10:40:05 info: [MCP][User: 6755f8a647fbe36db6ef2ec0][ngrok] Establishing new connection
2025-04-29 10:40:05 info: [MCP][User: 6755f8a647fbe36db6ef2ec0][ngrok] Creating SSE transport: https://[removed].ngrok-free.app/mcp/sse
2025-04-29 10:40:05 info: [MCP][User: 6755f8a647fbe36db6ef2ec0][ngrok] Establishing new connection
2025-04-29 10:40:05 info: [MCP][User: 6755f8a647fbe36db6ef2ec0][ngrok] Creating SSE transport: https://[removed].ngrok-free.app/mcp/sse
2025-04-29 10:40:05 info: [MCP][User: 6755f8a647fbe36db6ef2ec0][ngrok] Connection successfully established
2025-04-29 10:40:05 info: [MCP][User: 6755f8a647fbe36db6ef2ec0][ngrok] Connection successfully established
2025-04-29 10:41:31 info: [api/server/controllers/agents/client.js #checkVisionRequest] not implemented
2025-04-29 10:43:00 error: [api/server/controllers/agents/client.js #sendCompletion] Operation aborted 422 Failed to deserialize the JSON body into the target type: messages[6]: invalid type: sequence, expected a string at line 127 column 4
2025-04-29 10:43:00 error: [api/server/controllers/agents/client.js #sendCompletion] Unhandled error type 422 Failed to deserialize the JSON body into the target type: messages[6]: invalid type: sequence, expected a string at line 127 column 4

Screenshots

No response

Code of Conduct

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

[danny-avila]

Which tool are you using, is it returning an image? More information is needed.

[danny-avila]

If you can, also, export the conversation as JSON from the top right while viewing it.

[danny-avila]

Actually, I think I see the issue, it's widespread with Deepseek and was handled before but not with a case-sensitivity:

cline/cline#230

[StefanRichterHuber]

The tool just generates JSON (or YAML for tests) output

[danny-avila]

Try updating now, follow the directions here: https://www.librechat.ai/docs/local/docker#update-librechat

[danny-avila]

Closed by #7132