Manifest error codes

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

[🦚 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	No `Authorization` header on the request
M002: Empty Bearer token	Header present, token after `Bearer` is blank
M003: Invalid key format	Token doesn’t start with `mnfst_`
M004: Key expired	Key past its expiration date
M005: Key not recognized	No matching agent for this key

Providers (M100–M101)

Your key is fine, but no provider credentials are wired up. See Routing and API key providers.

Code	What
M100: Provider API key missing	Routing picked a provider you haven’t connected
M101: No providers configured	Agent has zero providers connected

Limits (M200–M204)

You hit a usage cap, rate limit, or Free plan request quota. M200-M203 surface as HTTP 429. M204 surfaces as HTTP 402 because it is a billing plan restriction.

Code	What
M200: Usage limit exceeded	Cost or message-count limit you set was crossed
M201: Per-user rate limit exceeded	More than 200 requests/minute from one user
M202: Per-IP rate limit exceeded	More than 500 requests/minute from one IP
M203: Concurrency limit exceeded	More than 10 in-flight requests at once
M204: Monthly request limit reached	Free plan monthly request quota was exhausted

Request validation and model selection (M300–M302)

M300-M301 mean the request body is malformed and surface as HTTP 400. M302 means the request named a direct model that is not available for this agent; Manifest returns it as a friendly proxy message.

Code	What
M300: Missing messages array	Body has no `messages` array, or it’s empty
M301: Messages array too long	More than 1000 messages in a single request
M302: Model not available	Explicit model ID is not available for this agent

Server (M500)

Manifest itself broke. Surfaces as HTTP 500.

Code	What
M500: Internal server error	Unhandled error in the proxy pipeline

Getting Started

Deployment

Features

Providers

Reference

Manifest error codes

Authentication (M001–M005)

Providers (M100–M101)

Limits (M200–M204)

Request validation and model selection (M300–M302)

Server (M500)

​Authentication (M001–M005)

​Providers (M100–M101)

​Limits (M200–M204)

​Request validation and model selection (M300–M302)

​Server (M500)

Authentication (M001–M005)

Providers (M100–M101)

Limits (M200–M204)

Request validation and model selection (M300–M302)

Server (M500)