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

Goes well beyond the readOnly/idempotent annotations: each match carries qualifying figures, sample sizes, and a page URL; uncheckable districts are 'counted, not hidden'; and when nothing matches it returns near-misses sorted closest-first with the ruling-out criterion. The flats-retirement caveat is also disclosed. This is rich operational context.

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 purpose followed by criteria enumeration and then the two valuable behavioral clauses (uncheckable districts, no-match fallback). The criteria list partially duplicates the schema, but the description stays readable and most sentences carry non-redundant information.

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 12-parameter, no-required, no-output-schema tool, it explains the AND-combination semantics and the return payload (figures, sample sizes, URLs, near-miss fallback), so the agent knows what comes back. Only the interaction/precedence among the six sibling tools is left unaddressed.

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 all 12 parameters thoroughly (including enums, ranges, sort defaults). The description mostly re-lists the same criteria, adding only the houses-only qualifier for the price comparison. Baseline 3 is appropriate.

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?

Opens with a specific verb and resource ('Find the London postcode districts') plus the conjunctive screening model ('meet several open-data criteria at once'). This clearly separates it from siblings like find_london_district, rank_london_districts, and compare_london_districts without the agent needing to open schemas.

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 'meet several criteria at once' (AND-filter screening), and it does state one constraint ('Houses only'). But it never names when to prefer rank_london_districts or compare_london_districts, which is a real risk given six siblings. No explicit when-not guidance.

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