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

No annotations, so the description carries the full burden, and it does substantial work: it discloses the pay-per-call cost ($0.001 USDC on Base), the payment protocol (x402/MPP), and the concrete behavior that a 402 challenge is returned on unpaid calls. It also describes the return shape (titles, years, links). Pagination and rate limits are not mentioned, which keeps it below 5.

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?

Two sentences, zero waste, and the core purpose and source are front-loaded. The payment caveat follows as a compact operational note rather than bloating the opening.

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 single-parameter search tool with no output schema, the description covers purpose, source, return fields, and the non-obvious payment requirement that an agent would otherwise stumble into via a 402 response. Nothing needed to invoke it correctly 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?

Only one parameter with 100% schema coverage, so the schema already satisfies the documentation need. The description's phrase 'matching a query' adds only marginal meaning that q is a free-text search string, with no syntax or format guidance.

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 ('Search UK legislation'), names the authoritative source, and enumerates the covered material (Acts and statutory instruments). This clearly distinguishes it from the caselaw_* siblings, which cover a different body of law.

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 establishes context clearly: this is for UK statute (legislation.gov.uk, the official revised statute book), which implicitly routes agents away from caselaw_search. It stops short of explicitly naming an alternative or stating when-not to use it, so no explicit exclusions.

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