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

With only readOnlyHint=true available, the description carries real extra weight: it discloses the data source, the returned fields (name, description, category, link, signals), and the meaning of those signals (auth: none/api_key/oauth, free_tier, https). It does not mention pagination, result-count defaults, or rate limits, so it is strong but not exhaustive.

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?

Front-loaded with the core purpose, then return shape, then filters – a sensible order with no filler sentences. It is a single dense block rather than cleanly separated sections, which slightly hurts scannability for a 6-parameter tool.

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 read-only discovery tool with no output schema, the description covers purpose, the search corpus, the exact fields returned, and the filter vocabulary. An agent has everything needed to decide to call it and construct a valid query.

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 83%, so the schema already documents auth, free, https, query and category. The description restates the same filters with example syntax (auth="none", free=true, https=true), which is mildly useful but adds little beyond the schema, and the 'limit' parameter is undocumented in both places.

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+resource ('Find a public API or data source') and names the backing corpus (1,500+ APIs on PublicAPIs.io). It clearly implies a search/discovery role that separates it from get_api and compare_apis, but never names a sibling explicitly, so differentiation is inferred rather than stated.

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?

Gives a clear trigger ('use this whenever the user (or your code) needs an API, dataset or third-party service') with concrete domain examples (weather, geocoding, payments, crypto prices). It offers no when-not guidance or explicit routing to get_api/compare_apis, so it stops short of a full 5.

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