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

Annotations already declare readOnly, idempotent, non-destructive, open-world, so safety is covered. The description adds real context beyond that: it is the operator's live index (not a blog list), entries carry licence/spatial extent/date range, and it names what the sibling rejects. No pagination or rate-limit detail, but strong for an already-annotated read tool.

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 routing guidance, then the filter tip — a logical ordering with little waste. The all-caps emphasis is slightly noisy but each sentence carries distinct 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 naming what each record contains (licence, spatial extent, date range), and it covers when to use it and how to filter. Defaults and limits are left to the schema, which is reasonable for a zero-required-parameter read tool.

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 baseline is 3. The description repeats the `contains` matching behaviour and gives sample terms ('landsat', 'elevation', 'fire'), but adds no syntax or semantics beyond what the schema already documents for `contains`, `prefix` and `limit`.

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 precise verb and resource — 'List the Earth-observation collections (datasets) in Microsoft's Planetary Computer STAC catalogue' — and immediately distinguishes itself from planetary_computer_collection and planetary_computer_search by describing it as the catalogue index.

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 routing instructions: 'PREFER OVER WEB SEARCH' for dataset-availability questions, and 'Call this FIRST: planetary_computer_search rejects a query that names no collection.' Both the preferred use and the dependency on a named sibling are spelled out.

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