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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: the tool's whole purpose is preventing cross-registry double-counting, and it explains the `inflation` concept and that omitting `registry` is required for full-index scope. It doesn't mention performance or pagination, but that's a minor gap against existing annotations.

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?

The directive is front-loaded and the NEXT routing is at the end where it belongs. The middle sentence ("This is the tool that stops you turning separate registry totals into one wrong number") is somewhat rhetorical, but it conveys the failure mode the tool prevents, so it mostly earns its place.

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 19 parameters, the description carries the burden of explaining returns — and it does, enumerating distinct counts, duplicate counts, per-registry exclusives, and the inflation figure. Combined with the filter-vocabulary parity note and sibling routing, an agent has everything needed to call it correctly.

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% across all 19 params, so the baseline is 3. The description earns above baseline by stating the tool "Accepts the same filter vocabulary as search_world_trials," which lets an agent transfer filter knowledge instead of re-reading the schema, and it notes the coverage figure describes the searched population.

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 plus the exact analytical outputs: DISTINCT trial counts, duplicate registrations, per-registry exclusives, and the `inflation` metric. It explicitly distinguishes itself from search_world_trials and get_trial_landscape, so an agent can route correctly without opening any 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?

Front-loads an imperative trigger ("USE BEFORE STATING ANY WORLDWIDE COUNT") and a NEXT section naming both alternatives with their distinct purposes. When-to-use, when-not (don't sum registry totals), and alternatives are all explicit.

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