Tools and streaming

Authoritative guidance on tool calling and streaming for the official OpenAI- and Anthropic-compatible endpoints exposed by KushRouter.

• OpenAI Chat Completions: POST /api/openai/v1/chat/completions
• OpenAI Responses: POST /api/openai/v1/responses
• Anthropic Messages: POST /api/anthropic/v1/messages

This guide intentionally follows the official OpenAI and Anthropic event styles.

OpenAI Chat Completions

• Tools declared via tools: [{ type: 'function', function: { name, description?, parameters? } }].
• Argument deltas stream at choices[0].delta.tool_calls[].function.arguments.
• Final-arguments fallback is emitted for providers that only send complete args at stop.
• stream_options.include_usage: true emits a final usage-only chunk before [DONE].

OpenAI Responses

• Tools declared with the Chat-compatible tools array.
• Non-streaming tool calls return status: "requires_action" with submit_tool_outputs.
• Streaming emits response.function_call_arguments.delta and .done.
• Terminal: response.requires_action or response.completed; usage may be included.

Anthropic Messages

• Tools declared via tools/tool_choice in Anthropic syntax.
• Streaming emits Claude-style SSE events including tool use blocks and input_json_delta.
• Usage fields include cache_creation_input_tokens, cache_read_input_tokens, input_tokens, and output_tokens.

Anthropic web tools support

Anthropic web tools are not supported on this endpoint. See the note here; for background, refer to this page’s guidance and event references.

Best practices

• Validate and sanitize tool outputs, treat arguments as untrusted JSON, implement idempotency/timeouts, prefer streaming for low-latency UX.

See also

• OpenAI Chat events
• OpenAI Responses events
• Anthropic events