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

The annotations already establish that this is a read-only, idempotent, non-destructive, closed-world lookup. The description adds meaningful context beyond the annotations by stating that the result includes an NPI and that this NPI is needed by check_coverage, which helps the agent understand the tool's role in a multi-step workflow.

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?

The description is a single efficient sentence. It front-loads the lookup action and then adds the downstream dependency on check_coverage without any 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?

For a simple two-parameter read-only lookup with full schema coverage and informative annotations, the description supplies enough context to invoke the tool correctly. It identifies the key output, NPI, though it does not describe how multiple doctor matches are returned, which is a minor gap for a search tool.

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 the schema already documents both required parameters: zip as a 5-digit ZIP near the doctor and query as the doctor's name. The description reinforces the ZIP-based location lookup but does not add syntax or matching semantics beyond what the schema provides.

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?

The description uses a specific verb and resource: "Look up a doctor near a ZIP code," and states the useful output, the doctor's NPI. It also distinguishes this lookup from the downstream sibling tool check_coverage by saying the NPI is "needed by check_coverage."

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 gives a clear usage context by tying the tool to check_coverage: use it to obtain an NPI needed by that tool. It does not provide explicit when-not guidance or name other alternatives, but the intended workflow is clear.

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