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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description goes beyond these by stating 'US only', 'Returns up to 25 matches', 'Verified source: IRS EO BMF', '7-day cache', and includes a feedback mechanism. This adds valuable behavioral context without contradicting the annotations.

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 paragraph but includes multiple pieces of necessary information: purpose, parameters, return fields, usage guidance, source, cache, and feedback. While it is somewhat long, each sentence contributes to the overall clarity. The key purpose is front-loaded, so it remains effective.

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?

The description covers the tool's purpose, parameters, return fields, limits, data source, cache behavior, and a feedback fallback. With an output schema present, no additional return-value details are needed. It is complete for an agent to invoke correctly.

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 100% and the schema already describes both parameters. However, the description adds meaning by specifying that 'name' can be 'Full or partial organisation name' and that 'state' 'defaults to all states', which are not in the schema. This enhances understanding of parameter semantics.

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 clearly states the tool searches US nonprofits by name with an optional state filter, specifying the verb 'Search', the resource 'US nonprofits', and the scope 'by name'. It also explicitly distinguishes this from the sibling tool nonprofit_fetch_nonprofit_by_ein, making the purpose 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 gives explicit guidance on when to use this tool versus the alternative: 'Use this when you have a name but not the EIN. Use nonprofit_fetch_nonprofit_by_ein instead when you have the exact EIN for a precise single lookup.' This provides clear when/when-not conditions.

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