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

Annotations already flag readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful non-schema context: a $0.15 per-call price paid in USDC on Base via x402, which affects whether an agent should call it. It stops short of describing the response shape or failure modes (e.g. invalid postcodes).

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, front-loaded with the verb and scope, no filler. The long enumerated list of metrics and rankings is dense but each item carries information; it could have been grouped slightly better but nothing is wasted.

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 3-parameter read-only tool with no output schema, the description tells the agent what data comes back (prices, yields, crime, flood) and how it is ranked, plus cost. Remaining gap is output structure and error behavior, which is minor given the annotations.

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 coverage is 100%, so all three parameters including defaults are already documented. The description reinforces the districts format ('2 to 5 ... comma-separated' is in the schema) and ties the crime/flood dimensions to the crime flag, but adds no meaning for months or the effect of toggling crime off.

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?

Specific verb (Compare), specific resource (UK postcode districts), explicit scope (2 to 5 side by side), and an enumerated set of dimensions and rankings. An agent can tell this is a multi-district comparison tool, distinct from the single-topic siblings property_area, property_flood and property_rents.

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?

Usage is implied by the scope: reach for this when you need several districts compared at once, and the ranked outputs hint at decision-support queries. However, it never states when to prefer property_area, property_flood or property_rents instead, and gives no prerequisites or limits beyond the 2–5 count.

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