mcp_session_message
A mcp_session_message is an artifact MCP Gateway creates for every tool call it routes. Each one records what ran, why, and how it went. Arguments and results are not stored.
A mcp_session_message belongs to a mcp_session — the session groups all call records from one agent run. The session_id field on each record is the reference back to that session.
session_id
The ID of the mcp_session this call record belongs to. Use it to group all records from the same agent run.
sequence_number
The call’s position in its session, starting at 0.
tool_name
The tool that ran, without its namespace prefix.
server_slug
The server or platform surface that answered.
rationale
The agent’s own explanation of why it made the call.
outcome
ok if the tool answered, input_required if the call relayed a question to a person, or error if it did not.
duration_ms
Total call time, measured at the gateway.
upstream_ms
How long the server took to answer, not counting connection time.
connect_ms
How long connecting to the server took. With upstream_ms, this is the server’s share of the call’s time; the rest is what Atlan spent checking access and routing the call. Present only when the gateway recorded the split — a tool Atlan answers itself, or an older record, carries the total in duration_ms only.
error_class
A coarse failure category for a failed call. Never contains the downstream response.
protocol_version
The MCP protocol revision the call used.
traceparent
The W3C trace context the client sent, which links the call to your agent’s trace.
mcp_elicitation_event
What the call did with a question for a person: asked relayed one, answered carried the person’s answers back, and refused did not relay it. Present only on a call that took part in one.
mcp_elicitation_chain
One ID every call of that question’s exchange shares, so you can follow it across rounds.
mcp_elicitation_round
The call’s round in that exchange, starting at 1.
mcp_elicitation_action
The person’s decision on that round’s questions: accept, decline, or cancel.
See also
- Track usage and audit tool calls: View sessions and calls in MCP Gateway studio.
- Supported features and limits: Audit trail API and recording limits.