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

Beyond the read-only, idempotent, non-destructive annotations, the description adds important behavioral context: the data comes from the official daily public extract, contact/PII fields are never ingested, and it discloses credit costs plus preview row and daily-call limits.

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 dense but front-loaded with the resource and returned fields, then adds source, exclusions, query semantics, and cost details. Every sentence contributes useful information without repetition.

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?

It gives a strong high-level picture and lists returned fields in lieu of an output schema, but for a 23-parameter tool with no schema descriptions, it does not explain how most filters should be used. This is adequate for a bare call but incomplete for filtered queries.

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 0% across 23 parameters. The description explains only that q searches all text fields and that filters combine with AND, leaving the meaning, accepted values, and formats of nearly every filter undocumented.

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 resource and scope: every registered and removed charity on the Charity Commission register for England and Wales, including the fields returned. This clearly distinguishes it from sibling tools such as query_uk_companies and query_uk_insolvency.

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?

It provides clear context for use: filters combine with AND, q searches all text fields, and it explains credit costs and preview limits. It does not explicitly say when to use a different tool or list alternatives, so it falls short of a 5.

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