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

Annotations already cover read-only, idempotent, open-world, non-destructive behavior, so the bar is lower. The description adds a genuinely useful scope caveat — 'a structural comparison only, never an efficacy or safety ranking' — which prevents an agent from presenting the output as a comparative judgment.

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?

Two short sentences, zero filler, with the primary scope (what is compared) front-loaded and the critical limitation immediately after. Nothing needs trimming.

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 one parameter, no output schema, and rich annotations, the description covers what is needed: what is compared and what the output must not be read as. The main remaining gap is that it does not state the identifier format required for nct_ids.

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?

There is one parameter with 0% schema description coverage, but the description partially compensates by stating the accepted count range of 2 to 5 studies, mirroring minItems/maxItems. It does not explain that the values must be NCT identifiers or match the strict NCT\d{8} pattern, so meaning is only partly added.

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 names the operation (side-by-side comparison), the resource (registry attributes), and the scope (2 to 5 studies), which is enough to distinguish it from the retrieval siblings like get_clinical_trial. It stops short of explicitly naming which sibling to use instead, so it lands at 4 rather than 5.

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?

Usage is implied by 'Side-by-side ... for 2 to 5 studies' — an agent can infer this is for multi-trial comparison rather than single-trial retrieval. However, it never names an alternative tool or states when not to use this one, so guidance is inferential only.

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