> ## Documentation Index
> Fetch the complete documentation index at: https://manifest.build/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Manifest error codes

> Reference for every Manifest proxy error code (M001-M500). What you saw, why it happened, and how to fix it. Covers auth, providers, limits, validation.

When Manifest blocks or rejects a request, the response message starts with a code in square brackets:

```text theme={"theme":{"light":"github-light","dark":"github-dark"}}
[🦚 Manifest M100] No anthropic API key yet. Add one here: https://app.manifest.build/...
See https://manifest.build/docs/errors/M100
```

Look up the code below to see what it means and how to fix it.

## Authentication (M001–M005)

These fire when the bearer token on `/v1/chat/completions` is missing or wrong. They surface as HTTP 401 to non-chat clients.

| Code                                               | What                                           |
| -------------------------------------------------- | ---------------------------------------------- |
| [M001: Missing Authorization header](/errors/M001) | No `Authorization` header on the request       |
| [M002: Empty Bearer token](/errors/M002)           | Header present, token after `Bearer ` is blank |
| [M003: Invalid key format](/errors/M003)           | Token doesn't start with `mnfst_`              |
| [M004: Key expired](/errors/M004)                  | Key past its expiration date                   |
| [M005: Key not recognized](/errors/M005)           | No matching agent for this key                 |

## Providers (M100–M101)

Your key is fine, but no provider credentials are wired up. See [Routing](/routing) and [API key providers](/providers/api-key-providers).

| Code                                           | What                                            |
| ---------------------------------------------- | ----------------------------------------------- |
| [M100: Provider API key missing](/errors/M100) | Routing picked a provider you haven't connected |
| [M101: No providers configured](/errors/M101)  | Agent has zero providers connected              |

## Limits (M200–M203)

You hit a usage cap or rate limit. They surface as HTTP 429. See [Set limits](/set-limits).

| Code                                               | What                                            |
| -------------------------------------------------- | ----------------------------------------------- |
| [M200: Usage limit exceeded](/errors/M200)         | Cost or message-count limit you set was crossed |
| [M201: Per-user rate limit exceeded](/errors/M201) | More than 200 requests/minute from one user     |
| [M202: Per-IP rate limit exceeded](/errors/M202)   | More than 500 requests/minute from one IP       |
| [M203: Concurrency limit exceeded](/errors/M203)   | More than 10 in-flight requests at once         |

## Validation (M300–M301)

The request body is malformed. They surface as HTTP 400.

| Code                                          | What                                        |
| --------------------------------------------- | ------------------------------------------- |
| [M300: Missing messages array](/errors/M300)  | Body has no `messages` array, or it's empty |
| [M301: Messages array too long](/errors/M301) | More than 1000 messages in a single request |

## Server (M500)

Manifest itself broke. Surfaces as HTTP 500.

| Code                                        | What                                  |
| ------------------------------------------- | ------------------------------------- |
| [M500: Internal server error](/errors/M500) | Unhandled error in the proxy pipeline |