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

Annotations already declare read-only, idempotent, non-destructive, but the description adds what they cannot: no auth or API key required, data freshness (refreshed daily), and a hard result ceiling of 10 matches with the fields returned. That is exactly the operational context an agent needs before calling.

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 purpose, cost, and source, then parameter routing. The quoted query-phrase list is longer than strictly necessary but functions as concrete routing signal rather than filler.

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?

There is no output schema, and the description compensates by naming the returned fields and the 10-match cap. Combined with the auth, freshness, and parameter-combination notes, an agent has everything needed to call it correctly and interpret the result.

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 the baseline is 3, and the description goes beyond it by stating the two valid parameter combinations (first + last, or organization, each with optional state) and clarifying that organization is the alternative rather than an addition. It does not explain the trailing-* wildcard behavior, which stays in the schema.

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 and resource (NPI lookup in the CMS NPPES registry) plus scope (free, refreshed daily). The name/entity distinction is spelled out, so an agent can tell this apart from verify_npi or check_npi_status without opening the 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?

Gives concrete triggering phrasings and the exact input shapes for person vs. business searches, including the 'do I already have an NPI' case. It never names or excludes the sibling tools (verify_npi, check_npi_status, search), so the boundary between a lookup and a verification is left to inference.

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