List the terrain Hydrata can fetch for a site

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

Annotations already declare readOnly/idempotent/non-destructive, yet the description adds genuine behavior: results are ordered finest-first, only sources with non-zero coverage are returned, Copernicus GLO-30 always appears, and oversized requests are surfaced via cap.state and a plain message. The row-field enumeration overlaps with the output schema, which is the only reason this isn't 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?

Front-loaded with purpose, then the ordering constraint, then the workflow instruction — good structure with no filler. The middle enumeration of row fields ('key', 'name', 'resolution_m', ...) is long and partly duplicates the output schema, costing a point.

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?

An output schema exists, so return-value detail is optional; the description still supplies what the agent needs to act (which field to pick, what 'coverage_pct' means, how to handle 'too_large'). The only loose end is the mention of `say_to_user`, which is not among the listed sibling tools.

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 both parameters are documented there, so the description adds little parameter detail. It only obliquely ties 'your box' to bbox via coverage_pct; no added semantics for project_id or the bbox format.

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+resource ('List the terrain sources') plus an ordering guarantee ('finest resolution first'). It is clearly separable from sibling tools that upload terrain (presign_terrain_upload, finalize_terrain_upload) or consume a source key (create_terrain_from_source).

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?

Explicit sequencing guidance: 'Ask this BEFORE fetching or uploading your own DEM' names the alternative path (uploading a DEM) and its preconditions. It also names the downstream tool (create_terrain_from_source) and the selection rule ('Pick one whose cap.state is ok'), leaving no inference to the agent.

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