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

Annotations already declare readOnly, idempotent, non-destructive, open-world, so the safety profile is covered. The description earns credit by disclosing what is actually assembled: the operator URL vs. the catalogue's stable latest-version URL, licence, bbox, publication status, and the cross-linking of a realtime feed to its GTFS Schedule parent plus sibling realtime streams — behavior not inferable from annotations or schema.

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 and scope, then a single dense enumeration of returned fields; no filler sentences. It is one long run-on clause chain, so a short list of returned fields would scan faster, but nothing is wasted.

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?

With no output schema, the description takes on the burden of describing returns and does so comprehensively — URLs, licence, contact, bbox, declared features, status, and the realtime/schedule relationship. Combined with the id format guidance, an agent has everything needed to call it correctly.

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% and there is a single parameter, so the baseline is already high. The description still adds value by giving id format variants ('mdb-1210, or a jbda-* id'), where the schema example only shows the mdb-* form.

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 — fetch everything recorded about one transit feed by catalogue id — and immediately distinguishes itself from mobilitydb_search_feeds by requiring an exact id rather than search terms. An agent can tell the two apart without opening either schema.

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 scope ('one feed, by catalogue id') clearly implies this is the detail-view follow-up to a search, and the schema reinforces that by saying the id is 'Shown as `id` by mobilitydb_search_feeds.' It does not explicitly state when-not to use it or name the sibling tools (search_feeds, gtfs_rt_feeds) in the description itself, so a small inference is required.

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