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

No annotations are provided, so the description carries full burden. It discloses that results are always ordered by readiness score, that filtered category calls create a 'discovery receipt' supporting provider-funded actions and explicit interest, and that unfiltered browsing does not enter the demand cohort. This is substantive behavioral context, though terms like 'discovery receipt' and 'Stage 1 demand cohort' are not fully explained, which slightly reduces clarity.

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 two sentences long, front-loaded with the core purpose. The first sentence states what the tool does and the optional filter; the second adds necessary nuance about ordering and behavioral implications. No wasted words.

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?

Given the tool has no output schema and no annotations, the description covers essential aspects: purpose, optional filtering, ordering, and behavioral side effects. It does not describe the response format, but for a simple top-sites list with only two parameters, the description is largely sufficient. Minor gaps include undefined jargon and missing details about default limit behavior, but these are partially mitigated by the schema.

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 baseline is 3. The description adds semantic value beyond the schema by explaining the behavioral consequence of using the category parameter: it creates a discovery receipt and enables provider-funded actions, whereas omitting it keeps browsing free. This extra context goes beyond the schema's basic 'filter by public category' and elevates the score.

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 clearly states the tool retrieves 'the highest-scored agent-ready sites in the index' with an optional category filter. The verb 'Get' and specific resource ('sites in the index') are explicit, and the 'optionally filtered by category' differentiates it from sibling tools like search_agents, which likely returns broader search results.

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 provides clear context on when to use the tool: to retrieve top-scored sites, with an optional filter. It explains the behavioral difference between filtered and unfiltered calls (filtered creates a discovery receipt supporting provider-funded actions, unfiltered stays free), which informs when a category should be used. However, it does not explicitly mention alternatives or state when not to use this tool in favor of a sibling.

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