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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds meaningful behavioral context beyond those flags: it lists exactly what data is returned, notes the cap of 'up to 10 study locations,' and identifies the underlying ClinicalTrials.gov v2 API source.

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 description is a single dense sentence that front-loads the action and the required identifier, then compactly enumerates the returned fields and source. Every sentence earns its place without 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?

The parameter is fully documented in the schema, an output schema exists, annotations cover safety and idempotence, and the description itself covers return content, limits, and data source. Nothing essential for correct invocation is missing.

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 single parameter nct_id already has 100% schema description coverage, including pattern and an example. The description repeats the example and format without adding substantial new meaning, so it correctly stays at the baseline for high schema coverage.

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 opens with a specific verb and resource: 'Retrieve full details of a specific clinical trial by its NCT identifier.' It also enumerates the major fields returned, making it easy to distinguish from sibling tools like clinicaltrials.trials.search, recruiting, and stats.

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 description clearly implies when to use this tool: when the agent already has an NCT identifier for a specific trial. It does not explicitly say 'use search when you don't have an NCT ID' or name alternatives, so it stops short of full alternative routing.

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