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

Annotations already flag destructiveHint=true and idempotentHint=true, so the bar is lower, and the description still adds real value: the source is discarded, the tab disappears, and there is no implicit fallback to the active composition. It does not cover error behavior if the id is stale, which keeps it from 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?

Three short sentences, front-loaded with the action and its consequence, followed by the intended scenario and the failure-mode caveat. No repetition of the title and no 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 two-parameter mutation with no output schema and annotations already declaring the destructive/idempotent profile, the description covers what an agent needs to call it correctly. The only minor gap is what happens when the id is invalid or already closed.

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?

With 100% schema coverage the baseline is 3, but the description adds meaning beyond the schema: the id must be explicit and is never inferred from the active composition, clarifying a semantic the schema's 'Required.' note does not convey. The token parameter's role is left entirely to the schema.

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 a composition') plus the concrete side effect ('removes it from the user's tabs; its source is not kept'), which cleanly separates it from sibling list/inspect/update tools. An agent can distinguish it from delete_media or update_composition without opening a schema.

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?

'Meant for drafts made along the way' conveys the intended context of use, and 'never falls back to the active composition' warns of a failure mode an agent might otherwise assume. It stops short of naming alternatives or stating when not to close, so it is clear context rather than full routing guidance.

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