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

Annotations declare readOnlyHint=true and openWorldHint=false, so safety is covered, and the description goes further by disclosing the aggregation rule ('counts are never summed across registries — each registry's contribution is reported separately alongside the distinct total') and the deduplication semantics, which materially affect how the returned numbers should be interpreted.

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-loads the orienting directive before the return contents, and every sentence carries distinct information — outputs, aggregation caveat, and next steps — with no filler.

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 and no parameters, the description carries the full burden and discharges it by enumerating the returned counts, explaining the per-registry attribution rule, and pointing to the correct follow-on 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?

The tool takes zero parameters, so the baseline is 4. The description does add useful cross-tool context by explaining that the returned curated topic ids can be passed as `topic` to the other trial tools, which is a value-semantics note rather than a parameter definition for this tool.

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 (returns) and resource (trial corpus statistics) and enumerates exactly what comes back: source-record count, deduplicated canonical count, active count, per-registry attribution, and curated topic ids. It separates itself from siblings by naming search_world_trials and get_registry_sources as the follow-on tools.

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?

Explicitly says 'START HERE when orienting on the trial corpus' and then routes with 'NEXT: search_world_trials ... get_registry_sources ...' giving the agent a clear entry point and the conditions that select each sibling.

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