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

Beyond the readOnlyHint and idempotentHint annotations, the description adds valuable behavioral context: results are 'capped at 10,' no personal details are returned, 'no match request is created and nobody is contacted,' and the input is 'never stored.' This gives the agent a strong safety and privacy model beyond what annotations alone convey.

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?

The description is compact and front-loaded, starting with the core behavior and then adding key constraints (cap, no storage, no account needed, intended use case). Each sentence earns its place without redundancy 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 simple one-parameter read-only tool, the description covers everything an agent needs: return type, cap, privacy guarantees, lack of side effects, account requirements, and usage intent. No output schema exists, but the description fully specifies the return value ('a number and nothing else'), so context is complete.

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 description coverage is 100%, so the schema already documents the single 'description' parameter thoroughly. The tool description adds context about counting against the description, but does not need to compensate for missing schema information. Baseline 3 is appropriate.

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?

The description opens with a precise verb and resource: 'Count the people already in the pool whose situation is close to a description.' It further distinguishes this from sibling tools by emphasizing it 'saves nothing: no match request is created' and 'returns a number and nothing else,' making the tool's unique role clear.

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 description explicitly states when to use the tool: 'Use it to answer whether anyone is going through something similar, before the user decides whether to join.' It also notes this is the only tool that works without an account. However, it does not name sibling alternatives explicitly, so routing away from create_match_request is implied rather than spelled out.

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