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

Annotations already mark this as a read-only open-world lookup, and the description adds substantial behavioral context: pricing per successful call, x402 payment chains, and the fact that failed calls are not charged. It also discloses the flat-file KEGG REST source and a 100-gene cap, though it does not describe rate limits or failure modes.

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-loads what the tool returns before covering input, limits, and pricing. It is a dense paragraph rather than clearly structured sections, but every clause carries useful 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 an output schema present, the description need not explain return values, and it sufficiently covers source, input format, cap, and payment behavior. It is complete for calling the tool correctly, though it lacks sibling-usage guidance.

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 the pathway number and max parameter are already documented in the schema, including the default of 20. The description reinforces the pathway-number format and the 100-gene maximum but adds little beyond the structured field documentation.

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 verb: it retrieves KEGG human pathway details and the genes in that pathway, including which fields are returned. It is clear enough to distinguish from unrelated health tools, though it does not explicitly contrast itself with similar pathway or gene resources such as Reactome.

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 tells the agent the required input format (a five-digit human KEGG pathway number such as 05200) and the output cap, but it does not explain when to use this tool instead of a related pathway or gene tool. Usage is implied by the purpose rather than explicitly guided.

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