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

Annotations already declare readOnly, idempotent, closed-world and non-destructive, so the safety profile is covered. The description adds genuinely non-obvious behavior: values are case-sensitive and exact, and a wrong value yields zero results rather than an error, making failure indistinguishable from empty data. Only minor gap is that the response shape is described minimally (values plus counts).

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 sentences, front-loaded with what is returned, followed by the action directive and the failure mode. The concrete examples ("uk" not "UK", "AML / Financial Crime" not "AML") earn their space by making the case-sensitivity rule actionable.

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 parameters and no output schema, the description carries the burden of explaining returns, and it does: facet names plus per-value record counts. The silent-failure caveat covers the only remaining risk an agent faces when calling it.

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?

The tool takes zero parameters, so the schema baseline is 4. The description still adds useful meaning by framing the return values as the exact literals that must be reused verbatim in other tools, including worked casing examples.

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 and resource — returns every valid filter value with the record count carrying it — and enumerates the exact facets (jurisdiction, regulator, content types, topics, sectors, firm types, urgency levels, deadline types). This is clearly distinguishable from search/list siblings, which consume these values rather than enumerate them.

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?

"CALL THIS FIRST if you are unsure of any filter value" gives explicit when-to-use guidance, and the silent-zero-results warning supplies the cost of skipping it. The alternative behavior (calling a search tool directly) is implied clearly enough that an agent will not guess.

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