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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds real context beyond them: codes change yearly, the data version is returned, and CPT/dental/NDC/X12 remark codes are recognized but not described, which warns the agent about coverage gaps. It does not say how unrecognized or malformed codes are reported back, which is the main remaining ambiguity.

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 core check/validity behavior, then systematically covers inputs, coverage, and caveats. It is dense rather than padded, though the inline code examples repeat what the schema already lists and could be trimmed.

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 carries the return-value burden and does so reasonably: descriptor, chapter, plain-language note, data version, licensing notices. It still doesn't state the response shape per code (e.g., results aligned with input order, per-code status field), which is the one thing an agent might need to compose a follow-up call.

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 (codes array with 1-50 items, system enum) are already fully documented, and the description's examples largely duplicate the schema's own examples. It reinforces the "one call per statement" batching intent but adds no new meaning about how system values like 'auto' resolve.

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?

Names a concrete verb and outcome ("checks codes against the current official releases... reports whether each is valid, billable or terminated today") and enumerates the supported code systems. It is unmistakably a validity lookup rather than a free-text search, but it never names the sibling search_codes, so an agent still has to infer which of the two to pick for a code question.

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 direct routing guidance: "Use it for any code a user asks about" with concrete examples (Z00.00, 99213, J0696, CO-45) and the batching rule "Accepts every code from a statement in one call." It stops short of explicit when-not-to-use conditions or pointing to search_codes / check_eob_math as alternatives.

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