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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), so the bar is lower; the description still adds real value by disclosing the cost model (free within the daily allowance, then $0.001 USDC per call via x402) and by flagging that split wards are marked in the result. It says nothing about rate limits or failure modes on invalid codes.

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 tight sentences; the substantive scope statement is front-loaded and the pricing note follows. No filler or repetition of the title.

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?

An output schema exists, so return values need not be described, and the description still summarises the payload (wards plus local authorities) and the commercial terms. The gap is the absence of any guidance on what the single required code must look like or what happens for an unknown constituency.

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 description coverage ('ONS constituency code'), so the schema fully documents it and the description adds no format, prefix or validity detail. Baseline 3 applies when the schema does the heavy lifting.

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 specific resource and scope precisely: the wards (with split-ward flags) and local authorities composing a 2024 Westminster constituency. This distinguishes it from the other uk-geography siblings (county, ward, local-authority, lsoa), though it never names an explicit verb or notes that it operates on a single ONS code.

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, no indication of when to pick this over uk-geography__ward, local-authority or search, and no prerequisites such as needing a valid ONS code. The only contextual sentence concerns pricing, which is not usage guidance.

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