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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety bar is low; the description nonetheless adds real behavior: exact cross-registry dedup so duplicate registrations return once, deliberate exclusion of secondary aggregators (registry-authoritative but NOT a census), pagination driven by _meta.pagination with hasMore, and the evidence payload fields returned per result.

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 primary-use directive and organized under clear labels (HOW TO NARROW, SCOPE WARNING, PAGINATION, NEXT). It is dense and long, with some repetition of what the schema already states, but nearly every sentence carries actionable routing or workflow information.

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 23 optional params and no output schema, the description carries the full burden and does: it describes the per-result evidence payload (canonical id, normalized fields, source URLs, timestamps, checksums, citation block), explains pagination termination via hasMore, and points to the right follow-up tools. Nothing an agent needs to call it correctly 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?

Schema description coverage is 100%, so the baseline is 3, and the description does add meaning for several params: status="active" is defined as recruiting + active + not_yet_recruiting, `intervention` is framed as the modality separator, and `include="eligibilityText"` is flagged as a large payload. However, much of the registry and pagination guidance duplicates the schema text rather than extending it.

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+resource (search clinical-trial records) and precisely scopes it to the admitted primary registries (ClinicalTrials.gov and ISRCTN), with dedup semantics spelled out. It cleanly distinguishes itself from siblings like get_world_trial, get_trial_coverage and find_trial_registrations, 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?

Explicit when-to-use ("USE WHEN you need actual clinical-trial RECORDS for a disease, intervention, sponsor, country or date window"), an explicit scope warning about omitting `registry`, and named alternatives for adjacent needs (get_world_trial, get_trial_coverage, get_trial_landscape, find_trial_registrations). It even prescribes the narrowing workflow (q for disease, then intervention per modality).

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