nonprofit_fetch_charity_uk

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

Annotations already declare readOnlyHint, destructiveHint, idempotentHint, and openWorldHint. The description reinforces these with 'Read-only. No side effects. Idempotent.' and adds valuable context: 'UK only,' 'Verified source: UK Charity Commission OGL v3,' and '24-hour cache.' No contradictions.

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 listing key attributes, usage guidelines, and return values. Every sentence provides essential information without redundancy. It is concise yet comprehensive.

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?

Given the output schema exists, the description appropriately summarizes key return fields (registration status, income, etc.). It also covers caching, source verification, and provides a feedback mechanism, making it fully self-contained for an agent to use 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?

The input schema already documents the parameter, but the description adds format details ('7 digits, e.g. 1234567 or full/partial organisation name') and clarifies that it's required. This enhances understanding beyond the schema's description.

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 specifies the action ('Fetch'), the resource ('UK registered charity details'), and the input criteria (charity number or name). It explicitly distinguishes this tool from sibling tools for US nonprofits, 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 provides explicit guidance on when to use this tool (UK charities only) and when to use alternatives ('nonprofit_fetch_nonprofit_by_ein' or 'nonprofit_search_nonprofits_by_name' for US nonprofits). It also includes instructions for reporting gaps, ensuring proper usage.

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