# Open Responses Specification (/v1/responses)

Open Responses Specification is an agentic-web standard (endpoint — /v1/responses) at step 5, Act, governed by Linux Foundation; its status is "Published specification & conformance suite under Linux…". It answers: "How can an agent or application call LLM inference and server-side tool loops across multiple providers using a single…?" Replacing or extending OpenAI Chat Completions API, implementation status is multi-implementation (OpenAI, Hugging Face, Vercel, OpenRouter, Ollama…), last verified 2026-10-24.

## Quick Wire Reference
- **Step**: 5 Act (Do something for me)
- **Version**: 1.0 (2026-01-15)
- **Status**: Published specification & conformance suite under Linux Foundation ·…
- **Discovery / Probe Path**: /v1/responses
- **Spec URL**: https://www.openresponses.org/specification
- **Last Verified**: 2026-10-24 (current)
- **Classic Web Analog**: OpenAI Chat Completions API

[5 · Act](/category/act/)

| Open Responses Specification |
| --- |
| Category | [Act](/category/act/) |
| Also known as | openresponses, v1/responses |
| Web analog | OpenAI Chat Completions API |
| Originated by | OpenAI / Linux Foundation (2026-01) |
| Governed by | Linux Foundation (Open Responses project, seeded by OpenAI with Hugging Face, Vercel, OpenRouter, vLLM, SGLang, Ollama) |
| Form | endpoint |
| Track | Linux Foundation |
| Status | Published specification & conformance suite under Linux Foundation |
| Implementation | multi-implementation |
| Adopted by | OpenAI, Hugging Face, Vercel, OpenRouter, Ollama, vLLM, SGLang, LM Studio, LiteLLM, Anyscale |
| Version | 1.0 (2026-01-15) |
| Specification | [https://www.openresponses.org/specification](https://www.openresponses.org/specification) |
| Found at | /v1/responses |
| Acronym collisions | mcp, agent-protocol |
| Last checked | 2026-10-24 |
| Freshness | current · checked 2026-10-24 |
| Solves | Expose tools to agents, Let agents talk to other agents |

[Act](/category/act/) Open Responses is an open inference and agentic-loop API specification launched in January 2026 under the Linux Foundation, seeded by OpenAI’s Responses API (POST /v1/responses) with founding support from Hugging Face, Vercel, OpenRouter, Ollama, vLLM, SGLang, LM Studio, LiteLLM, and Anyscale [[1]](#ref-1)[[2]](#ref-2).

## Overview
Unlike legacy chat/completions endpoints that exchange stateless message arrays, Open Responses defines polymorphic items (message, function_call, function_call_output, reasoning), structured semantic streaming events (response.created, response.output_item.added, response.output_text.delta, response.completed), and multi-turn server-side tool execution loops (previous_response_id, hosted MCP tool calls, and client-side function calls) in a vendor-neutral OpenAPI 3.1 contract [[1]](#ref-1)[[2]](#ref-2).

## Discovery and probe

Published OpenAPI 3.1 contract or API documentation declaring POST /v1/responses · /v1/responses

```
POST /v1/responses
parse:     JSON response object with object="response" or streaming response.* SSE events
on absent: HTTP 404 or non-Open-Responses JSON payload
```

Not probed live: no-fixed-path. Open Responses defines the /v1/responses inference and tool-calling API schema rather than a public root discovery manifest.

## History
- 2026-10-24 — added to catalogue (v1.1.0 audit)

## Instances

Verified SDKs, reference implementations & validators:

- [openresponses/openresponses (reference OpenAPI 3.1 schema & compliance runner)](https://github.com/openresponses/openresponses) · implementation (2026-01-15)

## See also

- Pairs with: [Model Context Protocol](/protocols/mcp/), [Agent2Agent Protocol](/protocols/a2a/)

- Not to be confused with: mcp, agent-protocol

## References

- Open Responses launched in January 2026 under the Linux Foundation with OpenAI, Hugging Face, Vercel, OpenRouter, Ollama, vLLM, SGLang, and LM Studio as founding adopters. — [https://www.openresponses.org/specification](https://www.openresponses.org/specification) (2026-01-15) VERIFIED
- github.com/openresponses/openresponses hosts the normative OpenAPI 3.1 schema and conformance test suite for the /v1/responses agentic loop endpoint. — [https://github.com/openresponses/openresponses](https://github.com/openresponses/openresponses) (2026-01-15) VERIFIED

[JSON](/data/protocols/open-responses.json) · [Markdown](/protocols/open-responses/index.md) · [OKF v0.2](/okf/protocols/open-responses.md)