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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely non-obvious behavioral context: this is the AUTHORITATIVE source for product-level content and the extent of the EU archive, and that its id namespace diverges from other STAC catalogues. It omits auth/rate-limit detail, keeping it short of a 5.

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?

Three sentences, zero filler, each doing distinct work: what is returned, why the data is trustworthy, and how to get a valid id. Return-field detail is front-loaded ahead of the id caveat.

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 compensates by enumerating the returned fields, and the single required parameter is fully documented in the schema. Nothing an agent needs to call this correctly is missing.

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 the schema already supplies example ids, so the baseline is 3. The description earns above baseline by clarifying where valid ids come from and warning that ids are catalogue-specific, which is semantic guidance the schema cannot express.

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 (full detail for one collection) and enumerates the returned fields: title, description, licence, providers, spatial/temporal extent, asset keys. It also distinguishes itself from the sibling list tool copernicus_dataspace_collections, so an agent can choose between them 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?

Explicitly routes the agent to copernicus_dataspace_collections to obtain valid ids, and warns that Copernicus mission ids differ from ids used by other STAC catalogues for the same data. That is a concrete prerequisite plus alternative, with no inference required.

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