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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description adds useful non-schema behavior: a 20-result cap, citation-only return scope, and x402 pricing with failed calls not charged. Pricing and failure-charge policy are valuable behavioral details beyond the annotations, though it does not discuss rate limits or authentication mechanics.

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?

The description is compact and front-loaded: purpose and returned fields come first, then the citation-only limitation, result cap, and pricing. Every sentence carries useful selection or invocation 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?

Given the complete input schema, existing output schema, and read-only annotations, the description supplies the remaining context an agent needs: citation-only scope, result limit, and payment model. Nothing essential for correct invocation 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 both parameters are already documented in the schema, including q length bounds and max range/default. The description adds only the 'Up to 20 results' cap, which is redundant with the max parameter's 1–20 constraint, so baseline 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 verb and resource — PubMed search via NCBI E-utilities — and enumerates the returned citation fields (PMID, title, authors, journal, publication date, DOI). It also immediately clarifies that abstract text is not included, which prevents confusion about the resource being retrieved.

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?

It gives clear context for when to use the tool (PubMed article citation lookup) and explicitly excludes one case by saying 'no abstract text,' which is an important usage boundary. However, it does not name a sibling or alternative tool for full-text/abstract retrieval or for other biomedical literature searches.

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