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

Annotations already cover read-only, idempotent, non-destructive, and closed-world, so the bar is lower. The description still adds genuinely useful behavior beyond them: it discloses the return shape (matched excluded record(s) or a not-on-list result) and, critically, the coverage limitation that most LEIE records carry no NPI, which affects how the result may be interpreted.

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?

Three sentences, each carrying distinct load: what it does, what it returns, and the interpretive caveat. The verb and scope are front-loaded with no filler or repetition.

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 no output schema, the description correctly takes on the burden of describing return values and the meaning of a negative result. The remaining gap is minor: it does not say how multiple matching records are ordered or whether the result set is bounded.

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%, and both parameters (including the detail enum) are documented in the schema, so the description adds no parameter meaning beyond it. Baseline 3 applies; the mention of '10-digit' simply restates the schema pattern.

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 two-part verb (validate check digit, then look up in the NPI field of the LEIE mirror) against a named resource, which is far more precise than the title alone. It does not name or contrast itself with the sibling screening tools, so an agent must still infer the boundary from the NPI-only scope.

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 by the input (an NPI) and the closing caveat strongly hints that a not-on-list result should not be treated as clearance, which nudges toward other screening paths. However, it never says when to prefer check_npi over screen_exclusion or exclusion_list_status, so the routing decision 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.