Errors are a JSON object {type: "error", error: {type, message}, request_id}; the vendor code is error.type (e.g. authentication_error) and the request id also comes in the request-id header.

Claude API (Anthropic) · GET /v1/models · HTTP 401

Status: ✅ verified:server:prod · first seen 2026-10-31 · last confirmed 2026-10-31 · 1 confirmation from 1 vantage

What to do

No client-side fix known (by design).

Example

What probe af:anthropic:probe:no-key sends (prod) and what it checks in the answer.

GET https://api.anthropic.com/v1/models

Response (only what the probe asserts; other fields omitted):

HTTP 401
request-id: …
x-should-retry: false

{
  "type": "error",
  "error": {
    "type": "authentication_error",
    "message": "x-api-key header is required"
  },
  "request_id": "…"
}

In your code

When an SDK receives this response:

SDK	Raises	Check
Python `anthropic`	`anthropic.AuthenticationError`	`e.status_code == 401`
Node `@anthropic-ai/sdk`	`Anthropic.AuthenticationError`	`err.status === 401`

Read from the SDK source: anthropic 2.3.0: anthropic/_client.py Anthropic._make_status_error; @anthropic-ai/sdk 1.3.0: core/error.js APIError.generate.

Dimensions

env: prod · plan: any · region: any · account_state: anonymous

Evidence

Probe af:anthropic:probe:no-key (declarative, source)

Observations: none from reporters yet.

Related errors

invalid x-api-key · GET /v1/models · HTTP 401 authentication_error
x-api-key header is required · GET /v1/models · HTTP 401 authentication_error
invalid x-api-key · GET /v1/models/{model_id} · HTTP 401 authentication_error
x-api-key header is required · GET /v1/models/{model_id} · HTTP 401 authentication_error

Machine access

curl -s https://apifacts.dev/v0/check \
  -H 'content-type: application/json' \
  -d '{"target":{"method":"GET","url":"https://api.anthropic.com/v1/models"},"error":{"status":401}}'

YAML: facts/anthropic/error-envelope.yaml

Data: CC BY 4.0 · apifacts registry · This page is generated; edit the YAML, not the page.