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

Annotations already declare destructiveHint=true and idempotentHint=true, so the description's value is the specifics: the tab reloads, the headless runtime for that session is freed, and any in-flight export or render is interrupted. That is exactly the kind of consequence an agent needs before calling a destructive tool; only failure behavior (e.g. what happens if the project is not open) is left out.

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 tight sentences: the primary action and scope first, then the side-effect caveat. No filler, no restatement of the title.

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, no-output-schema tool with annotations covering safety, the description supplies the missing piece — what the destructive side effect actually is. Everything an agent needs to invoke it correctly is present, short of error conditions.

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?

Schema coverage is 100%, so both token and projectId are already documented in the schema. The description adds only an indirect hint about the token's session scoping ('this session's headless runtime'), which is baseline-level added value.

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 (close/release) and resource (the project session and its headless runtime), and names the concrete effect of returning the tab to the project manager. It is distinguishable from open_project/new_project by the release-of-runtime framing, though the description never names the sibling it complements.

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?

The 'releases this session's runtime' phrasing implies an end-of-session action, and the warning that a running export or render stops is a useful caution. But it never explicitly says when to call it versus leaving a project open, nor does it point to open_project for the reverse action.

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