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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered; the description adds genuinely non-obvious behavior: check-digit verification, per-call cost of $0.002 USDC via x402 on specific chains, and that failed calls are not charged. The only gap is no mention of result limits or pagination when searching by name.

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?

Front-loaded with the resource and its two modes, then capabilities, then cost — every clause carries information. The 'not medical advice' disclaimer is arguably boilerplate but is short.

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?

Output schema exists and annotations cover the safety profile, so the description only needs to convey modes, returned fields, and payment model — all present. Nothing an agent needs to invoke it correctly 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 coverage is 100%, so a 3 is the floor; the description adds real meaning by specifying the 10-digit format with check-digit verification for 'number' and clarifying that state is optional to the name search. It doesn't say what happens if both name and number are omitted or supplied together.

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 the specific resource (US healthcare providers from the NPPES NPI Registry), the two access modes (exact NPI lookup vs. name/state search), and the returned fields, which cleanly separates it from siblings like clinical_trials or fda_label.

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?

Explicitly lays out the two usage modes — 'look up one by its 10-digit NPI' or 'search by name with an optional state' — so an agent knows which parameter combination to pick. It stops short of naming an alternative tool for related healthcare data or stating when not to use it.

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