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

Annotations already cover readOnly/idempotent/openWorld/non-destructive, so the bar is lower; the description still adds real value by noting that metadata is keyless while the returned s3:// asset paths require a free Copernicus account, and that the upstream rejects a catalogue-wide search without collections.

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?

Purpose is front-loaded in the first clause, followed by the authoritative claim, the hard requirement, and caveats. The description is dense but each sentence carries distinct information; only the bbox restatement is redundant with the schema.

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 still describes the returned fields, notes the download auth requirement, flags the mandatory collections parameter, and confirms the bbox coordinate order. An agent has everything needed to invoke 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 description coverage is 100%, so the schema already documents every parameter including bbox orientation and the datetime interval format, which the description merely repeats. The account-requirement note concerns outputs rather than parameter semantics, so it adds no new parameter meaning beyond the structured schema.

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 ('Search the EU Copernicus archive for Sentinel and Contributing Mission products') and enumerates the return payload (product ids, sensing datetimes, footprints, asset inventory). It also distinguishes itself from the sibling collection-listing tools by naming copernicus_dataspace_collections as the way to obtain collection ids.

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?

Declares itself AUTHORITATIVE for 'which European satellite products cover this place on these dates', giving a clear selection context against other archive tools. It routes the agent to copernicus_dataspace_collections for collection ids, but does not state explicit when-not conditions.

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