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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety and open-world profile is covered. The description adds the useful 'Free' cost signal and tells the agent what the response contains (sites, filters, output fields), but it says nothing about latency, rate limits, or whether the data is cached or live.

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?

One tight sentence with the cost note front-loaded and the return contents enumerated in a natural order. Nothing is wasted, although the leading 'Free.' fragment is slightly abrupt and the example clause could be trimmed.

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 one-parameter, read-only metadata tool with no output schema, the definition covers what is returned (sites/stores, filters, output fields) and that the call is free. The remaining omission is guidance on when in a workflow to call it, which is a minor gap.

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 single enum parameter lists all eight valid service values explicitly, so the schema carries the parameter burden. The description only reinforces that it operates on 'one service'; 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?

The description states a concrete verb and resource: it returns supported sites/stores, extra filters and output fields for one service, with a concrete example about supermarkets and job boards. An agent can immediately tell this is a static metadata/discovery tool rather than a search tool, though it does not name a sibling such as list_services to differentiate itself from.

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 example ('which supermarkets or job boards can be searched') implies this is the tool to call before searching in order to learn available sites and filters, but there is no explicit when-to-use instruction, no when-not-to-use, and no reference to alternatives like list_services or the specific search tools.

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