---
title: "Look up an IETF RFC by number."
method: GET
path: "/api/dev/rfc"
tags: ["dev"]
---

# Look up an IETF RFC by number.

`GET /api/dev/rfc`

## Request

- Base URL: `https://2s.io`
- URL: `https://2s.io/api/dev/rfc`
- Auth: API key in header `PAYMENT-SIGNATURE`

Look up an IETF RFC by number. Pass number as RFC2616, 2616, or the integer 2616. Returns the RFC title, authors, publication date, status (e.g. INTERNET STANDARD, PROPOSED STANDARD, DRAFT STANDARD, INFORMATIONAL, EXPERIMENTAL, HISTORIC, BEST CURRENT PRACTICE), stream (IETF/IAB/IRTF/Independent/Legacy), DOI, canonical rfc-editor.org URL, and the full standards relationship chain: which RFCs this one obsoletes / is obsoleted by, and which it updates / is updated by. Authoritative data from the IETF/RFC Editor index. Use this to resolve whether a spec is current or superseded before relying on it.

## Query parameters

- `number` string, required
- `trial` 1

## Other responses

- `200` (unresolved $ref)
- `400`: Invalid request — not charged. error.code: BAD_REQUEST or INVALID_PARAM (parameter validation; error.details.issues lists each problem), MALFORMED_JSON, or a request-specific code. Other client errors: 405 METHOD_NOT_ALLOWED (wrong verb; see the Allow header), 413 PAYLOAD_TOO_LARGE.
- `402`: Payment required. Body is the x402 PaymentRequirements envelope with a multi-network accepts array; the per-call price is in accepts[].amount (and on the operation as x-2s-price). Sign for whichever rail you hold USDC on (EIP-3009 for Base, partial SPL transfer for Solana) and retry with the PAYMENT-SIGNATURE header (X-PAYMENT also accepted for v1 clients). Also PAYMENT_SETTLE_FAILED (error envelope) when a verified payment failed to settle: error.details.chargeStatus is "not_charged" (retry with a fresh payment) or "unknown" (the authorization may still settle before its deadline — check it before retrying).
- `429`: Too many requests — RATE_LIMITED: our per-IP / per-payer limiter. Not charged; retry after Retry-After.
- `5XX`: Server-side failure. 500 INTERNAL: unexpected error; quote error.errorId (also the X-2s-Error-Id header). 502 UPSTREAM_UNAVAILABLE (or another UPSTREAM_* code): the data provider failed — composite endpoints refuse unbilled when every source fails. 503 SERVICE_PAUSED: endpoint paused by the operator kill switch, retry after Retry-After; 503 SPEND_CAP: daily upstream budget exhausted. 504 UPSTREAM_TIMEOUT. Not charged.

---

[API](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api.md) · [All operations](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api/llms.txt) · [OpenAPI document](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api/revisions/da4c5caf686e?raw)