Errors
Tool errors your AI can act on, JSON-RPC errors, and the HTTP answers of Omni's MCP endpoint.
Tool errors
A tool that can't do what was asked answers normally, with isError: true, and a JSON object with an error code and a message: a plain sentence your AI can act on or pass on to you.
error | When | What to do |
|---|---|---|
space_not_found | The space_id doesn't exist, isn't yours, or this connection may not use it (including Personal when it wasn't allowed) | Call list_spaces and use an id from it |
invalid_arguments | A required argument is missing or empty, an argument isn't allowed, a value is too long, or a name is reserved | Fix the arguments |
not_editable | Changing what's fixed: anything about Personal, or the Inbox's name or persona | Leave it, or use another space |
no_files | A file tool on Personal | Use another space for files |
file_not_found | No file at that path | Call list_files |
invalid_path | Not a relative .md, .markdown or .txt path of allowed characters | Fix the path |
invalid_content | The file isn't UTF-8 text | Send text only |
limit_reached | A free limit: spaces, memories, files, file size, or actions per day | Tell the person; they can make room on the dashboard |
rate_limited | Too many calls in a short time | Try again in a minute |
not_saved | The memory couldn't be saved | Try again later |
tool_failed | Something went wrong on Omni's side | Try again later |
JSON-RPC errors
Problems with the request itself are JSON-RPC errors:
| Code | Meaning |
|---|---|
-32700 | The body isn't valid JSON |
-32600 | Not a valid JSON-RPC request. Send one message per POST; batches aren't accepted |
-32601 | Unknown method |
-32602 | Invalid params, an unknown tool or an unknown prompt |
-32002 | Resource not found |
-32020 | A header doesn't match the body (MCP-Protocol-Version, Mcp-Method or Mcp-Name, protocol 2026-07-28) |
-32022 | Unsupported protocol version; data.supported lists the ones Omni speaks |
HTTP answers
| Status | When |
|---|---|
200 | A JSON-RPC answer, including tool errors and most JSON-RPC errors |
202 | A notification was accepted |
400 | The request couldn't be read, or protocol headers are wrong |
401 | No token, or an expired or unknown one. The WWW-Authenticate header points to the OAuth metadata, so the app can sign in again |
403 not_allowed | The account isn't in early access yet |
403 origin_not_allowed | A browser page on a site Omni doesn't allow made the request |
404 | An unknown method, in protocol 2026-07-28 |
405 | GET or DELETE on /mcp. Omni answers POST only, with JSON, and has no event stream |
Protocol versions
Omni speaks MCP 2026-07-28 (stateless, with server/discover) and 2025-11-25, 2025-06-18, 2025-03-26 and 2024-11-05 (negotiated by initialize). It never issues a session id: every request stands alone.