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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior; the description adds genuinely useful context beyond those hints: public STAC catalog, no auth required, and a clear summary of what the response contains. This is exactly the kind of extra behavioral and access context an agent needs before calling.

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?

Two well-organized sentences: the first front-loads the action, scope, and return fields; the second compresses provenance, licensing, and auth into a compact clause. No filler or redundant restatement of the title.

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 simple two-parameter read-only lookup with an output schema, the description covers what the tool returns, where parameters come from, and access requirements. The only blemish is the upstream-tool name inconsistency (search_scenes vs. imagery.search), which could momentarily confuse an agent looking for the search sibling. Otherwise it is complete.

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%: both collection and item_id have descriptions with concrete STAC examples and the 'from a search_scenes result' provenance. The tool description only restates that provenance rather than adding new parameter-level meaning, so the high schema coverage carries the load.

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 action and resource: 'Get full metadata for one Sentinel satellite scene' and enumerates the exact returned fields (acquisition time, footprint, platform, cloud/snow cover, spectral band assets, thumbnail URL). The 'one scene' scope clearly distinguishes it from collection-level and search siblings.

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 description explicitly says Collection and item_id come from copernicus-sentinel.search_scenes, so an agent knows this is the post-search metadata-detail step. It also notes the data is public STAC with no auth required. It does not formally list exclusion cases or alternative tools, but the predecessor relationship is clear. Minor caveat: the named upstream tool doesn't exactly match the sibling list's copernicus-sentinel.imagery.search.

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