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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description meaningfully adds the cost and rate-limit model ('a few free samples a day, then $0.002 USDC per call via x402'), which an agent needs before invoking a paid endpoint. Return-format disclosure is unnecessary since an output schema exists.

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, and the scope statement is front-loaded ahead of the cost note. Every sentence carries distinct 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?

Safety, parameters, and return shape are covered by annotations, the schema, and the output schema respectively. The notable gap is sibling differentiation: with both pubmed__search and clinical-trials__search present, the description should say when this narrow clinical-trial-filtered endpoint is preferred.

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% and the schema documents the sole 'term' parameter including the '[pt] filter' hint. The description adds no syntax or semantics beyond the schema, so the baseline of 3 is appropriate.

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 states a specific resource and a narrowing scope: 'PubMed citations that are clinical trial reports for a query.' This functionally distinguishes it from the broader pubmed__search, though it never names that sibling explicitly. Purpose is clear, but routing between the two pubmed search tools still takes inference.

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?

There is no guidance on when to use this tool versus pubmed__search or pubmed__pmc-search, despite those siblings existing. The only conditional information given is the pricing model, which is not a usage-selection rule. An agent must guess based on the tool name alone.

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