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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive. The description adds valuable behavioral context: rate limit (30/min), no auth required, returns up to 25 results, uses ProPublica API, and specifies returned data (revenue, assets, health scores). This exceeds annotation coverage.

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 well-structured, starting with the core purpose, then details, then usage guidance. It is longer than minimal but every sentence adds value, including the feedback fallback. Could be slightly more concise but is efficient given the information density.

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 tool with 2 parameters, an output schema, and clear annotations, the description is comprehensive. It covers purpose, parameters (with mapping), limits, data returned, external API, rate limits, and usage flow. No significant gaps are present.

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 baseline is 3. The description adds significant value by explaining that category maps to NTEE codes, listing example categories, and noting that raw NTEE letters (A-Z) are also accepted. This clarifies the parameter semantics 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?

The description clearly states the tool's purpose: 'Search US nonprofits by mission category and state.' It specifies the resource (US nonprofits), action (search), and filters (category, state). It also distinguishes itself from siblings by positioning itself as a starting point for due diligence, with a follow-up tool mentioned (nonprofit_fetch_nonprofit_full_profile).

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 provides clear context for when to use this tool ('starting point for nonprofit due diligence') and explicitly recommends a follow-up tool for deep dives. However, it does not explicitly state when NOT to use this tool, such as when a direct EIN lookup is needed (handled by sibling tool).

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