API Overview

AnyRouter exposes four core inference surfaces — Chat Completions, Messages, Responses, and Embeddings — plus catalog and account endpoints. Most OpenAI-compatible tooling works by overriding the base URL and API key; Anthropic-compatible tooling uses the Messages endpoint.

Base URL

https://anyrouter.dev/api/v1

OpenAI-compatible clients that set the base URL to https://anyrouter.dev (and append /v1/... themselves) also work: /v1/models and /v1/chat/completions are the same API as /api/v1/....

All endpoints are versioned under /v1. Breaking changes bump the version (/v2) without removing older versions for a minimum 12-month deprecation window.

Choose an endpoint

Authentication: which key for which endpoint

AnyRouter uses two distinct API key families. Pick the right one for the endpoint you're calling.

flowchart LR
    App["Your app"]

    App -->|"sk-ar-…"| LLM["LLM API key"]
    App -->|"ak_…"| Mgmt["Management API key"]

    LLM --> Inference["Inference<br/>POST /chat/completions<br/>POST /messages<br/>POST /responses<br/>POST /embeddings<br/>POST /decisions"]
    LLM --> Read["Read-only<br/>GET /models<br/>GET /generation/:id<br/>GET /auth/key"]

    Mgmt --> Admin["Account admin<br/>/keys (CRUD)<br/>/management-keys<br/>/presets<br/>/auth/byok<br/>/credits"]

    classDef key fill:#fef3c7,stroke:#f59e0b,stroke-width:1px,color:#92400e
    classDef endpoint fill:#f1f5f9,stroke:#cbd5e1,color:#0f172a
    class LLM,Mgmt key
    class Inference,Read,Admin endpoint

Quick decision rule:

• I want a model to answer a prompt → sk-ar- LLM key.
• I want to create, rotate, or revoke keys / manage BYOK / read balances → ak_ management key.

See Management API Keys for the full scope catalog and management lifecycle.

Common headers

Endpoint summary

Error shape

All errors follow a consistent JSON envelope:

{
  "error": {
    "code": "payment_required",
    "message": "Upstream provider \"cloudflare\" returned 402 — insufficient quota",
    "metadata": {
      "type": "upstream_error",
      "upstream_backend": "cloudflare",
      "upstream_status": 402,
      "upstream_message": "You exceeded your current quota, please check your plan and billing details."
    }
  }
}

error.code is a stable machine-readable slug. The canonical set:

When AI Gateway BYOK rejects a call, AnyRouter parses the provider's verbatim message into error.metadata.upstream_message — that is the authoritative reason, not Cloudflare's wrapping text. See Errors for retry recipes and /docs/api for the full interactive reference.

Rate limits

Rate limits are enforced per-key. Every response carries at least:

X-RateLimit-Limit:     <requests per minute>
X-RateLimit-Window:    60
X-RateLimit-Tier:      <tier name>
RateLimit-Limit:       <same as X-RateLimit-Limit>
RateLimit-Policy:      <limit>;w=60

The per-minute tier does not emit X-RateLimit-Remaining or X-RateLimit-Reset — the edge limiter only reports the cap. The daily free-tier cap and Go's 5-hour window do emit Remaining / Reset (and matching RateLimit-* headers). See Rate Limits.

Tracing

POST /chat/completions and POST /responses also accept an optional request-body trace object:

{
  "trace": {
    "trace_id": "4f8c2b9670b44b49a2e71e7fd5c0b1d3",
    "trace_name": "checkout-flow",
    "span_name": "summarize-order"
  }
}

AnyRouter uses this metadata to correlate internal request steps such as identity resolution, rate-limit checks, upstream selection, and upstream dispatch. If you do not send a trace object, AnyRouter still returns an X-Request-ID header you can use for support.

Versioning

Changes are categorized as:

• Additive (new fields, new endpoints) — ship continuously, no notice.
• Deprecation — announced with a 12-month sunset window and a Deprecation response header.
• Breaking — land on a new /v2 path; /v1 remains available for the deprecation window.

Related

• Migrate from OpenAI — swap base URL and key
• Migrate from Anthropic — point Anthropic clients at Messages
• Migrate to Responses — adopt the structured lifecycle
• Errors — status codes and retry guidance