Who an NPI belonged to, as of a date

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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), and the description adds real behavior beyond them: it validates the NPI check digit first and returns the full version history rather than a single current record. It also gestures at a cross-reference with release data ('whether a hospital in the release discloses it'), which is disclosed behavior an agent could not infer.

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?

One front-loaded sentence that opens with the verb and resource before the return-field list, and the check-digit validation is tacked on at the end. Dense and mostly waste-free, though the trailing list of returned fields is slightly run-on.

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 needn't document return values, and annotations carry the safety profile; the temporal semantics and validation behavior round it out well. The phrase 'whether a hospital in the release discloses it' is the one mildly ambiguous element, implying a release cross-reference the agent has to guess at.

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 parameters (npi pattern, as_of YYYY-MM-DD with 'omit for current registration') are already fully documented. The description reinforces the temporal default but adds no syntax or constraint beyond what the schema provides — the baseline 3.

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 ('Look up a National Provider Identifier in the NPPES registry history') and enumerates the scope of what it returns (name, entity type, status, practice address, taxonomy, every version on record). No sibling tool touches NPIs, so the distinction from find_codes, get_payer_rates, etc. is unambiguous.

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?

The description makes clear when to use it — 'as of a date (or now)' — and what input framing it expects (a validated NPI). It never states a when-not condition or names an alternative, but no sibling overlaps this function, so the missing exclusion is low-cost.

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