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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context: the pricing model (free within a daily allowance, then $0.003 USDC per call via x402), which an agent needs to reason about cost of invocation.

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 short sentences with no waste; the returned-field inventory is front-loaded and the cost model follows. It is tight and readable, though it spends its first sentence enumerating return values that the output schema already conveys.

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 and rich annotations, the description need not explain return values or safety, and it usefully covers pricing. Remaining gaps are procedural rather than informational: nothing tells the agent how to obtain a valid identifier or when to prefer this tool over provision/changes.

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%, so the schema already documents type, year and number, including the regnal-year format for pre-1963. The description adds no parameter-level meaning beyond that, 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 the resource (an Act or instrument) and enumerates the returned fields (title, long title, date, status, extent, changes count, table of contents), so the agent can infer this is a metadata/overview fetch by identifier. However, it reads as a list of return values rather than a verb+resource action, and it never distinguishes itself from siblings like uk-legislation__provision or uk-legislation__changes.

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?

No when-to-use guidance and no routing to alternatives such as provision, changes, or search. The only implicit hint is the schema's 'see types' note pointing at uk-legislation__types, which helps identify the type code but says nothing about when this tool is the right choice versus its siblings.

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