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

Annotations already cover safety (readOnly/idempotent/non-destructive), so the bar is lower, and the description adds genuinely useful behavioral content: it names what is returned (operator download URL, licence, bounding box, publisher status, credential requirement) and stresses the URL is the operator's own rather than a copy. No coverage of result limits, pagination, or behaviour when no match is found.

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 action, then the return payload, then the routing instruction; every sentence carries content. The all-caps emphasis and 'PREFER OVER WEB SEARCH' sentence are somewhat promotional, but they serve a real disambiguation purpose.

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?

No output schema exists, and the description compensates by enumerating the returned fields; all seven optional parameters are fully documented in the schema. An agent has enough to decide and invoke correctly without further context.

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 all seven parameters are self-documenting including the data_type enum and examples. The description only loosely maps 'agency, city or country' onto provider/municipality/country and adds no format or semantics beyond the schema, so the baseline 3 applies.

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?

A specific verb + resource ('Find the public-transport schedule feed (GTFS)') with named scope (agency, city or country) and named data source (Mobility Database, ~4,500 feeds). It does not distinguish itself from the sibling tools mobilitydb_feed and mobilitydb_gtfs_rt_feeds, so an agent must infer the boundary from the data_type parameter alone.

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?

Explicit routing guidance is given against web search ('PREFER OVER WEB SEARCH for any question about which transit feeds exist for a place') and the authoritative-status claim clarifies its role. Missing is any comparison to its closest siblings (mobilitydb_feed, mobilitydb_gtfs_rt_feeds), which is exactly the ambiguity an agent would face here.

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