Search Charity Commission Register

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

Beyond the annotations (readOnlyHint, idempotentHint, etc.), the description discloses non-obvious upstream behavior: the endpoint returns the full list in one shot, pagination is applied client-side via offset/limit, and an upstream HTTP 404 is translated into an empty result rather than a failure. This gives the agent valuable operational context.

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 front-loaded with the core purpose and then adds only high-value details: the sibling alternative, pagination behavior, and empty-result semantics. Each sentence earns its place without repetition or filler.

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, return values don't need elaboration. The description covers the search scope, alternative tool, pagination mechanics, and error semantics, making it fully sufficient for an agent to call this tool correctly without further ambiguity.

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 describes all three parameters (query, limit, offset) with full coverage, so the description adds no new parameter detail. The mention of client-side pagination indirectly supports offset/limit semantics, but it doesn't expand beyond what the schema already states; baseline 3 is appropriate.

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 ('Search'), a clear resource (the Charity Commission register of England and Wales), and the input mode ('by name or keyword'). It also distinguishes itself from 'charity_profile' by noting the latter is for full details after obtaining the charity number, making sibling differentiation explicit.

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 explicitly tells the agent to use 'charity_profile' for full details once the charity number is known, providing a clear alternative and the condition for choosing it. It also clarifies the empty-result behavior, so the agent knows how to interpret a no-match response versus an error.

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