[BUG] Tool calling fails

[tsterbak]

Quick Summary

Whenever a tool is called it failes:
"""agent: LLM call failed {agent_id=main, iteration=1, error=failed to parse JSON response: failed to decode response: json: cannot unmarshal object into Go struct field .choices.message.tool_calls.function.arguments of type string}"""

Environment & Tools

• PicoClaw Version: v0.2.1
• AI Model & Provider: llama.cpp Qwen3.5-35B, configured as openai integration
• Operating System: RaspberryOS
• Channels: Telegram

📸 Steps to Reproduce

1. Ask for the weather
2. It fails

❌ Actual Behavior

agent: LLM call failed {agent_id=main, iteration=1, error=failed to parse JSON response: failed to decode response: json: cannot unmarshal object into Go struct field .choices.message.tool_calls.function.arguments of type string}

✅ Expected Behavior

Works

💬 Additional Context

Not sure what else to provide. Maybe I'm just doing something wrong? I just dropped the new version in for the previous v0.2.0, where it worked.

[nikolasdehor]

There's a fix PR for this: #1292 (fix(openai_compat): accept object tool call arguments).

The root cause is in pkg/providers/openai_compat/provider.go line 211:

Arguments string `json:"arguments"`

The OpenAI spec says arguments should be a JSON string, but llama.cpp (and some other local inference servers) send it as a raw JSON object instead. Go's JSON decoder fails because it can't unmarshal a JSON object into a Go string field.

The fix in PR #1292 likely changes the Arguments field to accept both formats. The idiomatic approach is using json.RawMessage:

Arguments json.RawMessage `json:"arguments"`

Then in the parsing logic (line 250-253), handle both cases:

• If it's a quoted string: unmarshal the string first, then unmarshal the JSON within
• If it's a raw object: unmarshal directly into map[string]any

This is a common compatibility issue with OpenAI-compatible servers (vLLM, llama.cpp, Ollama in some modes) that don't stringify tool call arguments. The fix should be backwards-compatible since valid JSON strings would still work.

[tsterbak]

Sounds good :)