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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds meaningful context beyond them: this is the operator's live index, it is authoritative about 'exactly which ids' are valid, and callers get licence/extent/date-range metadata. It does not discuss the 1-500 limit or pagination, which is a minor gap.

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 purpose, then the routing preference, then the filter hint — a logical order with no filler. It is dense and long for a listing tool, but every sentence carries routing or scoping information.

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 stating the per-collection fields returned (licence, extent, date range) and the role the results play (ids to feed into earth_search_search). For an optional-parameter, read-only listing tool this covers what an agent needs 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 description coverage is 100% and the schema already documents limit (1-500, default 50), prefix, and contains with matching examples. The description's `contains` examples ('sentinel', 'landsat', 'dem') duplicate rather than extend that, 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?

Specific verb ('List') plus resource (satellite collections in Element 84's Earth Search index), with the concrete contents enumerated (Sentinel-1 GRD, Sentinel-2 L1C/L2A, Landsat C2, NAIP, Copernicus DEM) and the fields returned (licence, extent, date range). An agent can distinguish this from the sibling earth_search_search, which it explicitly references.

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 instructs to PREFER this over web search for a defined question type ('which free, no-account satellite imagery is available') and names the downstream alternative (earth_search_search) that consumes the ids this tool produces. When-to-use and what-to-do-next are both stated.

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