responses-api

# Responses API Reference The OpenAI Responses API (`POST /v1/responses`) is the recommended API for agentic workloads. Launched March 2025. Chat Completions is NOT deprecated, but superseded for new projects. **Sibling protocols in the `inference-apis` plugin.** Backend support for Responses is far thinner than for **`chat-completions-api`**, which remains the lingua franca every server implements — check that skill before assuming a target speaks Responses, and for the translation seam when it doesn't. The Anthropic-protocol equivalent is **`messages-api`**. Three protocols, one question: which surface does this backend actually serve? Codex CLI dropped Chat Completions in Feb 2026; most major clients (OpenCode, Continue.dev, Cline, Zed, Roo-Code, Vercel AI SDK 5+) now default to Responses. 10 backends serve `/v1/responses` — **Llama Stack is the only non-OpenAI backend with `/v1/responses/compact`**. Full adoption timeline and per-client status in `references/adoption.md`. **Last refreshed**: 2026-07-19. ## Key Differences from Chat Completions | Aspect | Chat Completions | Responses API | |--------|------------------|---------------| | Input | `messages[]` with `role`+`content` | `input` (string or `InputItem[]`) + `instructions` | | Output | `choices[0].message` | `output[]` array of typed `OutputItem`s | | Tool defs | `tools[].function.{name,params}` (nested) | `tools[].{type,name,params}` (flat, `strict:true` default) | | Tool calls | `message.tool_calls[].functi...