Documentation Index
Fetch the complete documentation index at: https://docs.ai-stats.phaseo.app/llms.txt
Use this file to discover all available pages before exploring further.
Tool calling lets models request structured actions (for example, database lookups, weather checks, or internal API calls) instead of guessing answers.
The Gateway supports tool payloads across these text endpoints:
/v1/chat/completions (OpenAI-style tools and tool_calls)/v1/responses (Responses-style function_call output items)/v1/messages (Anthropic-style tool_use blocks)
Request
curl https://api.phaseo.app/v1/chat/completions \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "openai/gpt-5-nano",
"messages": [
{ "role": "user", "content": "What is the weather in London?" }
],
"tools": [
{
"type": "function",
"function": {
"name": "get_weather",
"description": "Get current weather by city",
"parameters": {
"type": "object",
"properties": {
"city": { "type": "string" }
},
"required": ["city"]
}
}
}
],
"tool_choice": {
"type": "function",
"function": { "name": "get_weather" }
},
"stream": false
}'
Response
{
"id": "chatcmpl_...",
"object": "chat.completion",
"choices": [
{
"index": 0,
"finish_reason": "tool_calls",
"message": {
"role": "assistant",
"content": null,
"tool_calls": [
{
"id": "call_123",
"type": "function",
"function": {
"name": "get_weather",
"arguments": "{\"city\":\"London\"}"
}
}
]
}
}
]
}
{
"tools": [
{
"type": "gateway:datetime",
"parameters": {
"timezone": "Europe/London"
}
}
]
}
parameters.timezone is optional and must be a valid IANA timezone.timezone can also be provided as a top-level shortcut on the tool object.- The result contains ISO datetime plus the resolved timezone.
- Usage includes
usage.server_tool_use.datetime_requests.
- Prefer
tool_choice: "auto" so the model can decide when to call it.
Current limitation
At the gateway request-contract layer, stream: true with tools currently returns 400 invalid_request with:
Streaming with tools is not supported. Set stream to false when tools are present.
For now, run tool-calling requests with stream: false.
Next guides
- Tool Calling Patterns
- Tool Calling Safety and Validation
- Structured Outputs
