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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds data provenance ('open-data figures') and clarifies that the hub/commute column is optional, but omits freshness, aggregation caveats (e.g. 'main borough's' rent roll-up), and any rate/coverage limits.

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 the core scope (side-by-side, 2-6 districts, London baseline) before the metric list, and every token is informative. It is a single long run-on sentence, which slightly hurts scannability of the metric list but wastes nothing.

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 no output schema, the description carries the return-value burden and does so well by enumerating the metric columns, the London-wide baseline, and the optional commute column. It would be stronger with a note on output shape (per-district rows) and data recency, but it is largely sufficient for correct invocation.

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%: districts, hub and bedrooms are all documented inline, including the 2-6 item bound and the enum values. The description only echoes '2 to 6 districts' and the optional hub commute, adding no syntax or format meaning beyond the schema, so 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?

The verb 'compare' (side-by-side) plus resource 'London postcode districts' is specific, and the enumeration of metrics leaves no doubt what the tool computes. It implicitly separates itself from single-district tools like get_district_profile and ranking tools like rank_london_districts via the '2 to 6 districts and London as a whole' scope, but never names a sibling explicitly.

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 only implied: the side-by-side framing and multi-district scope suggest this is the tool for cross-district comparison. There is no explicit when-to-use/when-not, and no pointer to get_district_profile (single area) or rank_london_districts (ordered ranking) as the alternatives an agent should weigh.

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