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

Annotations already declare this a non-destructive, non-idempotent mutation, and the description adds real value on top: what survives the operation ('Artifacts and replies remain'), that disconnecting is not equivalent, and the re-entry semantics. It does not say whether the session becomes permanently unusable or what the call returns, so it falls short of a 5.

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?

Four short sentences, the primary action front-loaded, then progressively finer caveats. Every sentence carries distinct information (persistence, re-entry, disconnect caveat) with no repetition or filler.

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?

For a one-parameter mutation tool with no output schema and annotations covering the safety profile, the description supplies the key behavioral facts an agent needs: persistence of artifacts, non-equivalence with disconnect, and re-entry. Only the meaning of session_id and the post-call state of the session are left unaddressed.

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?

The single required session_id has 0% schema description coverage and is never mentioned; the description instead talks about a 'self-declared name,' which hints at the identity model but does not map cleanly to the parameter. It adds conceptual meaning about session identity, so it is not a 1, but an agent gets no help on what to pass to session_id.

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 action on a specific resource: 'Close this recorded visit.' Combined with the contrast to mere disconnection and the re-entry note, an agent can tell this apart from the 'enter' sibling without opening the schema. It is somewhat figurative ('recorded visit') rather than plainly worded, which keeps it just under 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?

'Disconnecting alone does not record a leave' gives an explicit when-to-use trigger and implicitly rules out relying on disconnect. 'Enter again later with the same self-declared name' sketches the enter/leave pairing, though it never names the 'enter' tool directly or states any prerequisites. Clear context, but no explicit exclusion list.

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