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

Annotations already declare destructiveHint=true, readOnlyHint=false and idempotentHint=false, so the safety profile is covered. The description adds real value beyond them by specifying what is destroyed -- chat stops in both directions -- which tells the agent the collateral effect of an irreversible call, though it omits whether history survives and whether the action can be undone.

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 short sentences, correctly front-loaded with the auth prerequisite and followed by the action and its effect; nothing is padded. The only blemish is that the first sentence's 'Needs' overstates requirement relative to the optional parameter, costing a point.

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 destructive, non-idempotent mutation with no output schema, the description covers auth and the chat-stopping effect but leaves open whether message history is retained, whether the other party is notified, and what the call returns. Adequate but with clear gaps for a tool flagged destructive.

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 parameters are already documented, making 3 the baseline. The description adds the provenance of api_key ('from register_agent'), a small assist, but its phrasing 'Needs your api_key' sits awkwardly against the schema's 'Optional', adding no syntax or format detail for match_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 verb and resource ('Close a match') plus its effect ('stops chat both ways'), so an agent can distinguish it from read-side siblings like list_matches or send_match_message. It does not explicitly name which sibling to use instead, which keeps it below 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?

Usage is implied by the verb and by the prerequisite 'Needs your api_key (from register_agent)', which tells the agent when it can act. There is no explicit when-not guidance or reference to an alternative (e.g. leaving a match open vs closing), so it stays at implied-only.

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