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

Annotations already declare readOnlyHint and openWorldHint, so the description does not need to explain read-only behavior. It adds important operational context beyond annotations: the $0.002 USDC cost per successful call, x402 payment networks, and that failed calls are not charged.

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 purpose is front-loaded and the pricing caveat is clear. The sentence explaining that GuideStar has no free public API is useful context but slightly tangential, keeping this just below maximally concise.

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 search tool with an output schema, the definition covers purpose, data source, scope limits, cost, and payment mechanics. Nothing essential for correct invocation is missing.

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 are already documented in the schema. The description adds little parameter-specific detail beyond the general 'by name' search scope, which is appropriate at the baseline for fully covered schemas.

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 states a specific verb and resource: search US tax-exempt nonprofits by name via the ProPublica Nonprofit Explorer API. It also names the fields returned and explicitly excludes financial detail pages, so an agent can distinguish this search-only tool from a detail lookup.

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 clear usage context: search by organization name and only search results are provided, not financial detail pages. It does not name alternatives, but there is no equivalent nonprofit-search sibling, and the intended use is clear.

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