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

# Errors

> The user-facing error codes you can hit through the MCP connector, and what to do about each one.

Every error Sumvin returns carries a short code, so an agent or a person can tell one failure from
another without parsing prose. This page covers the codes you can actually meet on the paths this
documentation covers — the MCP connector and the account setup it depends on. It isn't the full list
Sumvin's systems use internally.

## Reading a code

A code has three parts, and sometimes a fourth: `DOMAIN-STATUS-SEQUENCE`, then `-R` if the failure is
worth retrying.

* `MCP-401-001` — the area (`MCP`), the HTTP status it came with (`401`), and which failure in that
  area (`001`). No `-R`, so it's **terminal**: sending the same request again gets the same answer.
  Something has to change first — the credential, the input, a setting.
* `MCP-429-001-R` — ends in `-R`, so it's **retryable**: the same request, sent again after a short
  wait, can succeed without anything changing. Honour `Retry-After` when the response carries one,
  and back off between attempts.

That's the whole rule, so a client can decide without a lookup table: retry when the code ends in
`-R`, stop otherwise.

| Code            | Meaning                                                                                                                                                           | What to do                                                                                                 |
| --------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------- |
| `MCP-429-001-R` | Too many requests from this connected agent in the current window.                                                                                                | Wait for the time in the response's `Retry-After` header, then retry. See [Limits](/reference/mcp/limits). |
| `MCP-429-002-R` | Too many requests from this network address in the current window, before an agent was even identified.                                                           | Same as above — wait for `Retry-After`, then retry.                                                        |
| `MCP-403-002`   | The tool called isn't one this connection serves. Covers three different reasons — see [Refusals](/reference/mcp/refusals) for which applies and what to do next. | Read the refusal's own text; don't retry blind.                                                            |
| `MCP-401-001`   | The connection's credential wasn't accepted.                                                                                                                      | Reconnect the agent — this isn't something a retry with the same credential fixes.                         |
| `MCP-403-001`   | The connection's credential doesn't cover what was asked.                                                                                                         | Nothing to retry; the account holder needs to grant a wider connection.                                    |
| `MCP-503-001`   | The connector isn't set up in this environment.                                                                                                                   | Not something an agent or account holder can fix, and retrying won't change it.                            |
| `MCR-503-001`   | Signing a Stamped Mandate isn't set up in this environment — the browser page it hands off to has no address configured.                                          | Not something an agent or account holder can fix, and retrying won't change it.                            |

<Tip>
  A code starting `MCP-4` or `MCR-4` names something about this specific request (wrong credential, wrong
  tool, rate limit). The two `-503-001` codes above mean the service isn't configured here — they have
  no `-R`, because retrying won't help until someone sets it up.
</Tip>