Errors

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.
`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 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.

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.

MCP server

CLI

Status and errors

Reading a code

​Reading a code

Reading a code