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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is free. The description adds genuinely non-obvious traits: results are aggregated and ranked descending rather than raw rows, domain coverage is structurally limited, and returned entities are internal lookup values that must not be cited directly — the underlying regulation/bill/actor record should be cited instead. Return-shape details are omitted, but an output schema exists to cover that.

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?

It is front-loaded — the aggregation purpose and the 'instead of paging' rationale come first, then parameters, then exclusions, then provenance. The data-sources paragraph is longer than strictly necessary but earns its place by establishing that entities are non-citable, which prevents a downstream citation error.

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 read-only aggregation tool with a full schema and an output schema, nothing actionable is missing: what is counted, how it is ranked, the supported domain universe, the window and country filters, and a citation caveat are all present. The explicit list of unsupported domains removes the main failure mode for this 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 coverage is 100%, so baseline is 3. The description still adds operational meaning beyond the schema: domain is required and selects which activity is counted, since/until bound the counting window (with a 'last 10 days' example), and country_code is comma-separated with an omission rule. Only country_id's deprecated status is left entirely to the schema.

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 specific verb and resource — an aggregated, descending-ranked count of regulations/consultations per issuing entity — and explicitly contrasts it with paging raw rows client-side, which distinguishes it from siblings like list_regulations and list_entities. An agent can tell exactly what this returns without opening the schema.

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?

It names the question patterns this answers ('most active entities', 'who issued the most regulations') and gives an explicit negative case: bills/news/schedules/votes/actors/interventions/transcripts are not supported and still require paging plus manual synthesis. It also says to omit country_code for all accessible countries, so both when-to-use and when-not-to-use are covered.

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