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

Goes well beyond the readOnlyHint/openWorldHint annotations by disclosing a per-call price ($0.002 USDC), the payment rail and protocol (x402 on Base/Solana/Arc), and a billing rule that failed calls are not charged. It also caps output volume ('up to 20 genes per call'), which materially affects how an agent should interpret results.

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 sentences, both dense and front-loaded: payload contents first, then scope exclusion, limits, and payment terms. No filler, no restatement of the title, and the licensing/attribution note is compact.

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, return-value detail is not required, and the description instead covers the things the schema cannot: exclusions (prevalence), volume limits (20 genes), licensing, and the paid-call mechanism. For a single-parameter read tool this is fully sufficient to call correctly.

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?

Only one parameter and schema description coverage is 100%, so the schema already documents the ORPHAcode format and example. The description confirms the tool is keyed on ORPHAcode but adds no new constraint such as valid-range or lookup-failure behavior. 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?

States a specific verb+resource ('Orphanet rare disease by ORPHAcode') and enumerates exactly what is returned: preferred name, synonyms, disorder group/typology, and associated genes with association type. It also states what is NOT returned (prevalence), so an agent knows the payload boundary without opening the output schema.

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: look up a rare disease record when you have an ORPHAcode. There is no explicit when-to-use versus alternatives guidance and no sibling tool is named, though the sibling list contains no other Orphanet tool, so confusion risk is low. The 'prevalence is not included' note is a useful scope exclusion but not a routing rule.

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