Supported features and limits - Atlan Documentation

Use this page to check whether MCP Gateway fits your clients and servers before you connect them.

Client to gateway

Capability	Support
Transport	Streamable HTTP at `https://api.atlan.com/mcp`
MCP protocol revisions	`2026-07-28` (stateless, no handshake) and `2025-11-25` (with `initialize`), on the same URL
Authentication	OAuth 2.1 with protected-resource discovery (RFC 9728), or an `Authorization: Bearer` token
`tools/list`, `tools/call`	Supported
Progress notifications and cancellation	Relayed between the client and the downstream server
Trace context	A W3C `traceparent` in `_meta` is recorded and forwarded downstream
`prompts/list`, `prompts/get`	Supported for Atlan’s own authoring recipes
`resources/list`, `resources/read`	Supported for Atlan’s own resources under `atlan://defaults/`
Standalone GET/SSE stream	Not supported
`notifications/tools/list_changed`	Not sent. Run `tools/list` again to see catalog changes.
Sampling, elicitation, and tasks	Not supported

Gateway to your MCP servers

Capability	Support
Transport	Streamable HTTP over `https://` or `http://`
stdio servers and legacy HTTP+SSE servers	Not supported
Servers hosted by Atlan	Not supported. Atlan connects to a server you run.
Tools	Discovered, catalogued, and proxied
Prompts and resources from your servers	Not proxied
Private network addresses	Blocked. Loopback, private ranges, link-local, and cloud metadata addresses are refused, and redirects are not followed.
One server per URL	Registering the same URL twice is refused.

Credentials for your servers

Credential	How the gateway uses it
None	Calls the server without credentials.
Bearer token	Sends it in `Authorization`, or in a header you name.
API key	Sends it in the header you name, with an optional prefix.
Basic auth	Sends it in `Authorization`.
OAuth 2.0 client credentials	The gateway gets and renews the access token. The client secret never reaches the MCP proxy.
Per-user OAuth	Each person connects their own account. The gateway discovers the server’s sign-in and registers itself automatically, using PKCE.

A server uses either one shared credential or per-user OAuth, not both. Certificate and SSH-key credentials are not supported. The gateway injects a single header per server.

Governance

Capability	Support
Tool namespacing	`registry__`, `extension__<provider>__`, and `remote__<server-id>__` prefixes
Discover versus run	Reading a workspace lets you see its servers’ tools. Updating it lets you run them.
Enable or disable	Per server. A disabled server’s tools leave the catalog.
Per-tool and per-agent allowlists	Not available
Session and call audit	Every call inside a session, with rationale, outcome, and duration
Argument and output capture	Not stored, by design
Rate limits	Per account and per account per server. A refusal returns `-32003` with `retry_after_seconds`.

Catalog limits

Limit	Value
Automatic catalog refresh	Every hour, and on register, test, or refresh
Downstream call timeout	10 seconds by default
Tools discovered per server	Up to 10,000
Tool list size per server	Up to 8 MiB
Tool name pattern	`^[a-zA-Z0-9_-]{1,128}$`

Errors your client may see

Error	Meaning
`-32602` with `reason: uncatalogued`	The tool is not in the catalog. Run `tools/list` again.
`-32003` with `data.reason`	Access was refused. `never_connected` and `needs_reconnect` mean you need to connect your account. `token_rejected` and `audience_mismatch` mean the credential does not match the server.
`-32003` with `rate_limited`	Wait for `retry_after_seconds`, then retry.
`session_id is required`	Call `registry__initialise` and pass its `session_id`.

When a server needs your sign-in or cannot be reached, the gateway drops its tools from tools/list and names it in the result’s _meta, so the rest of the catalog still works.

​Client to gateway

​Gateway to your MCP servers

​Credentials for your servers

​Governance

​Catalog limits

​Errors your client may see