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

Annotations already declare read-only, idempotent, non-destructive behavior, so the bar is lower. The description adds real behavioral context beyond them: accuracy is bounded to postcode precision and it discloses that at a scheme edge, upcoming schemes are segregated under 'upcoming', and results carry a last-verified date. It does not mention rate limits or error behavior.

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?

Four sentences, front-loaded with what is returned and followed by caveats and input guidance; no filler. It is slightly dense and mixes return-format detail with usage guidance in the same breath, but every sentence carries 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?

An output schema exists, so return values need not be enumerated, yet the description nonetheless names the salient fields (dates, fee, source link, verification date, upcoming bucket). Combined with the precision caveat and the HMO guidance, an agent has everything needed to call this correctly.

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 baseline is 3, but the description goes further by explaining the joint role of occupants and households (settling the mandatory HMO test) and reiterating that address_line does not change lookup precision. That is genuine added meaning rather than restating the schema.

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 a specific verb and resource: looks up a postcode in HouseFile's council licensing records and returns schemes in force plus the national HMO rule. It also carves out its own scope against siblings by distinguishing in-force vs upcoming schemes, which maps onto upcoming_licensing_changes without opening either schema.

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?

Gives clear context for the conditional inputs ('Give occupants and households to settle the mandatory HMO test in England') and the precision limit where the answer degrades. It never explicitly names an alternative tool or states when not to use it, so routing against list_council_schemes or licensing_coverage is left to inference.

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