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

Annotations already cover readOnlyHint=true and openWorldHint=false, so the safety profile is supplied. The description still adds real behavioral value by enumerating the exact return contents (canonical trial, per-registry holdings, linking evidence, absences) and by warning that 'absence means absent from OUR index... not proof it was never registered there' — a crucial, non-obvious caveat consistent with the closed-world annotation.

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-loaded with the 'USE WHEN' trigger, then the mechanics, then the absence caveat, then the 'NEXT' routing. Every sentence carries actionable information and nothing is redundant.

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, the description fully compensates by describing what is returned and the semantics of absences, plus the downstream step. Everything an agent needs to invoke and interpret the tool correctly is present.

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% and the single 'id' parameter is already documented with examples. The description still enriches semantics by clarifying that any known identifier works and naming the supported namespaces (NCT, ISRCTN, EUCT, EudraCT), telling the agent the input need not be normalized to a specific registry.

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 (find) and resource (trial registrations) and precisely describes the input/transform: give one registry ID, get back the canonical trial, all registries holding it, the linking identifier evidence, and the registries where it is absent. It is clearly distinguishable from the sibling get_world_trial, which it names as the follow-up for the full record.

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?

Opens with an explicit 'USE WHEN' clause naming the trigger condition (holding ONE registry identifier) and the goal (determining whether it is the same study as another identifier, or where else registered). It also routes forward with 'NEXT: get_world_trial with the returned canonicalId', giving both context and the alternative path.

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