Use Ollama native tool calling: pass tools to /api/chat, execute the call, and return the result with role tool
domain: ollama.com · 5 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
POST /api/chat with tools: a list of {"type": "function", "function": {"name", "description", "parameters": <JSON schema>}} alongside model and messages.
If the model decides to call a tool, the response message has content "" and a tool_calls array: [{"function": {"name": "get_weather", "arguments": {"city": "Tokyo"}}}]. arguments is already a JSON object, not a string.
Execute the function yourself, then append two messages to history: the assistant message containing tool_calls, followed by {"role": "tool", "content": "<result text>", "tool_name": "get_weather"}.
POST /api/chat again with the extended history (keep the tools array); the model now answers in natural language using the tool result.
When streaming, tool_calls chunks arrive with done:false before the final done:true stats object.
Known gotchas
Only some models support tool calling (see ollama.com/search?c=tool); on non-tool models the tools list is ignored or answered in plain text.
The tool result message uses tool_name (not OpenAI's tool_call_id) to link the result to the call.
arguments in tool_calls is a decoded JSON object — do not json.loads it a second time (unlike OpenAI's string-encoded arguments).
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