brain-v42

Overview Schema Source Related Servers Discussions Admin

brain_session_resume

Read-onlyIdempotent

Resume an open session on explicit user command, reattaching a client to an existing session after verifying its expected client key.

Instructions

Resume an open session from an explicit user command.

An agent tracer is the only session the server opens or closes on its own; no hook and no auto-close may invoke this lifecycle boundary.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`session_id`	Yes
`expected_client_key`	Yes	Client identity expected for the addressed session UUID. The pair must match before any session mutation. This is an isolation guard, not authentication.

Output Schema

TableJSON Schema

Name	Required	Description
`session`	Yes	Persistent state of one explicitly controlled concurrent session.
`briefing`	No
`slot_closed`	No
`current_focus`	Yes
`open_session_count`	Yes
`current_focus_revision`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv0.6.7Oct 5, 2026
- addedOutput schema / properties / slot_closed
```
Added value: +{
+  "default": false,
+  "type": "boolean"
+}
```
First observedv0.6.1Sep 23, 2026

TDQS

B3/5.0

Behavior1/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations declare readOnlyHint=true and destructiveHint=false, yet the description calls this a "lifecycle boundary" that the server "opens or closes," and the schema states the client-key pair must match "before any session mutation." Resuming a session is an intentional state change, so the description directly contradicts the readOnly annotation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences with the primary action stated first and the lifecycle constraint second; no filler. Slightly cryptic phrasing ("agent tracer") costs it a point but the structure is sound.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need not be explained, and the description covers the invocation precondition (explicit user command). However, for a mutating lifecycle operation it omits what state changes on resume, error behavior for a closed/unknown session, and any detail on the undocumented session_id parameter.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is only 50%: expected_client_key is well documented in-schema, but session_id carries no description anywhere. The description adds no meaning about either argument (e.g., which session UUIDs are valid, what happens if the client key mismatches), so it fails to compensate for the coverage gap.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific verb (resume) and resource (an open session) and scopes it to explicit user commands, which separates it from the lifecycle-start path in siblings like brain_session_start. It does not name any sibling explicitly, so differentiation still requires inference from names alone.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

"From an explicit user command" gives a clear when-to-use trigger, and the second sentence effectively says when NOT to use it (no hooks, no auto-close). It stops short of naming the alternative to call for a brand-new session, so the routing guidance is good but not complete.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server