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

Annotations already declare destructiveHint=false, idempotentHint=true, and openWorldHint=false. The description adds meaningful scope beyond them: it only affects a grant-owned session and 'does not terminate unrelated processes', which is exactly the blast-radius information an agent needs. Return/pagination behavior is not described, minor for a close call.

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

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

Two compact sentences, with the usage trigger front-loaded ahead of the ownership/non-termination constraints. No filler, though the second sentence packs two distinct constraints without break.

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

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

No output schema exists, but for a close operation the essential agent needs (when to invoke, whose session is affected, what is NOT affected) are all present and the annotations cover the safety profile. Missing only explicit sessionId semantics, which keeps it from a 5.

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

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

One parameter (sessionId) with 0% schema description coverage, so the description must carry the load but says nothing about which session identifier to supply or its format. The UUID format in the schema partially compensates, leaving this at a minimum-viable 3.

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

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

States a specific verb and resource ('closes ... session') and scopes it to sessions 'owned by the authenticated grant', which an agent can distinguish from execution_session_open. It does not explicitly name a sibling or contrasting tool, so it stops just short of a 5.

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

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

Gives clear triggering conditions: 'when approved local work is complete or the user asks to stop using the current session.' It covers when to use it but offers no exclusions or comparison against alternatives like operation_cancel.

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