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

Goes well beyond the readOnly/openWorld annotations: pricing ($0.01 per call), the x402 USDC-on-Base payment channel and MPP HTTP endpoint, a 10-record cap, the non-obvious 'empty organizations is a paid 200' behavior, and an explicit disclaimer that no legal conclusion is computed.

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?

Dense but every clause earns its place, with no filler. Slightly imperfect front-loading: pricing and payment mechanics precede the actual purpose statement, so the agent parses cost before function.

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?

An output schema exists, so return values need no explanation. The description covers cost, payment rails, record limits, the empty-result edge case, and the legal disclaimer — everything needed to call and interpret this paid, open-world 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 coverage is 67% and already documents EIN stripping, exact-name matching, and the state limiter. The description reinforces 'exact organization name' and the EIN/name exclusivity but adds no syntax or format detail beyond 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+resource: 'IRS nonprofit status by EIN or exact organization name,' and enumerates the returned data (BMF exemption subsection, deductibility/foundation codes, Pub 78 listing, automatic revocations). This clearly separates it from siblings like entity_lookup and license_verify.

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?

Explains the two input modes (EIN or exact organization name) and that a name search can be limited by state, giving the agent clear context for invoking it. It does not, however, name sibling alternatives or state when a different tool is preferable.

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