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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false. The description adds valuable behavioral context beyond annotations: a daily free-sample quota and a per-call cost via x402. It does not detail how payment is authorized or what happens when the free quota is exceeded, but the cost disclosure is meaningful.

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, front-loaded with the purpose and followed by the cost model. Every sentence earns its place; there is no filler or repetition.

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?

Given a single required parameter, rich annotations, and an output schema, the description covers what the tool returns (article IDs) and the cost model. It omits usage context relative to sibling tools, but that is the main gap rather than a missing critical detail.

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% for the single 'term' parameter, which is documented as 'Query'. The description does not add any parameter-level semantics, so the baseline of 3 applies when the schema already carries the full burden.

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 resource and scope: 'Free full-text article ids in PubMed Central.' This differentiates it from sibling pubmed__search (general PubMed) and other PubMed tools by focusing on PMC full-text article IDs. The verb 'search' is absent from the description itself, though the tool name and title supply it.

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 explicit guidance on when to use this tool versus alternatives such as pubmed__search or pubmed__clinical-trials-search. The pricing model implies a paid search but does not state conditions for choosing this tool over siblings.

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