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

Annotations already declare readOnlyHint and openWorldHint, but the description adds materially new behavior: a $0.002 USDC charge per successful call via x402 on Base, Solana or Arc, with failed calls uncharged. That cost/settlement detail is exactly the kind of information an agent needs before invoking a paid tool and is not available anywhere in the structured fields.

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?

Front-loaded with purpose and returned fields, then the scope caveat, then pricing — a logical order with no filler. The pricing sentence is long but each element (amount, currency, protocol, supported chains, failure policy) is decision-relevant.

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?

With an output schema present, the description needn't explain return values, and it covers scope, the metadata-only limitation, and payment terms. The remaining gap is minor: nothing about result ordering or relevance ranking, though the rows parameter is fully schema-documented.

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%, with 'q' documented as 2-80 character search text and 'rows' as 1-10 results (default 5). The description only echoes the notion of a search term and adds no syntax, matching behavior, or format guidance beyond the schema, so the baseline 3 applies.

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?

States a specific verb and resource: UK government open datasets from the data.gov.uk catalogue via CKAN, and enumerates the returned fields (title, publisher, licence, last modified, resource count, link). It is clearly distinguishable from siblings such as gov_data_gov, gov_australia_data_gov_au, gov_canada_open_data, and the 'catalogue metadata only, not the data files themselves' clause prevents confusion with tools that return actual datasets.

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 ('for a search term') and an explicit scope limitation ('catalogue metadata only, not the data files themselves'), which tells an agent what this tool will and will not answer. It does not, however, name alternatives or say when to prefer a sibling national open-data tool, so it stops short of a full routing rule.

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