The OpenAI Interface

The inference contract every model host, router and local runtime speaks. OpenAI published an API; the industry turned it into a wire format, and a chat completion request written for one provider now runs against hundreds. This profiles that interface as it is actually implemented, grades it into tiers, and records who implements what.

Identifier	`openai-v1`
Originator	OpenAI
Cohort	reimplementation
Status	Published — 338 operations graded, 175 adopters recorded
Source of truth	openai/openai-openapi MIT Pinned at `38170fdddbb6a1813eae6c6587ee17cf2987185b` OpenAPI 3.1.0, info.version 2.3.0 — 215 paths, 338 operations. The upstream document moves weekly, so each profile release pins a commit SHA rather than tracking a branch.
Repository	https://github.com/api-commons/models

Conformance tiers

Every operation in the profile carries an x-tier. A compatibility claim is measured against a tier, not against the word "compatible".

Tier	What it covers
Core 2 operations	Measured, not chosen. POST /chat/completions is declared by 87.5% of the cohort and GET /models by 71.7%. Nothing else clears a third, so the tier boundary sits in a gap rather than at a threshold somebody picked.
Extended 19 operations	Declared by 5% to 50% of the cohort — embeddings (32.5%), the legacy completions endpoint (30.0%), image generation (23.3%), the Responses API (21.7%), audio, files and batches. This is where implementations diverge.
Vendor 317 operations	Under 5% of the cohort declares any of these — Assistants, ChatKit, Realtime, evals, and the whole organization administration surface. Effectively OpenAI-only in practice, and excluded from the profile OpenAPI by design.

Adopters

175 implementations recorded · as of 2026-09-13

Evidence	Count	Meaning
`declared`	101	Publishes their own OpenAPI, harvested byte-identical from their site, which declares operations in this profile. 15 reach the core tier and 52 reach extended; 34 declare part of the profile but not the whole core tier.
`vendor-matrix`	0	Publishes their own compatibility table. None harvested yet.
`prose`	74	States compatibility in their own words and publishes no spec we can read. Recorded, never promoted to a verdict.
`tested`	0	The conformance flow was run against a live endpoint. Not yet attempted — unlike open data and blockchain, this needs credentials and costs money.

The full adopter registry — every entry carries the URL it was read from and the date it was read.

Artifacts

OpenAPI — OpenAPI
The core and extended surface, self-contained, with x-tier on every operation.
Profile — Profile
All 338 operations, each with its tier and the evidence for that grading.
Overlay — Overlay
Stamps the tier grading onto the upstream OpenAI spec without copying it.
Arazzo — Arazzo
The flow that proves a core claim — list models, then use one.
MCP Tools — MCP
MCP tool definitions for the core tier.
Spectral Ruleset — SpectralRules
Lint any provider's OpenAPI and see which tier it reaches.
Adopter Matrix — Adopters
Generated — operation by adopter, across everyone who publishes a spec.

Licensing

The profile is independently authored from openly licensed machine-readable sources and public documentation; it does not republish a vendor's document. The upstream OpenAPI is MIT and carries its attribution. API Commons artifacts are CC BY-NC-SA 4.0 and code is Apache-2.0. "OpenAI" appears as a factual reference to the interface described, and nothing here implies endorsement.