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

Annotations already declare read-only/idempotent/non-destructive, but the description adds substantial behavioral context: the rate is weekly and must be converted with 52/12, resolution happens via BRMA rather than local authority, a separate lower shared-accommodation rate applies to under-35 claimants, and three distinct rate-setting bodies exist. This is exactly the beyond-structured-data context an agent needs.

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?

Content is front-loaded with the core meaning and then ordered by importance (unit trap, geography, postcode/room limits, providers). It is longer than strictly necessary — the 52/12 vs 4x arithmetic aside borders on over-explanation — but nearly every sentence carries decision-relevant 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?

Given a two-required-param tool with an output schema, the description is complete: it explains input constraints (full postcode, bedroom cap), the meaning of returned fields (rate_unit, brma, shared_accommodation_rate), and the free/no-auth nature. Nothing an agent needs to call it correctly is missing.

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 0%, so the description must carry parameter meaning, and it does: it requires a FULL postcode because a district cannot place a BRMA, and notes there is no category above 4 bedrooms, matching the enum values. It doesn't explain the enum labels individually, but the key semantics for both parameters are covered.

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+resource (retrieve Local Housing Allowance for a postcode/bedroom category) and frames its role concretely: the ceiling on housing benefit and effective rent floor. It also contrasts itself against siblings that provide rent figures (market_facts rental_value, listing monthly_rent), so an agent can place it without opening a 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 when the figure matters (benefit-funded tenancies, comparing against rent sources) and names the alternatives it should be used alongside. It stops short of explicit when-not-to-use guidance or naming a sibling tool by name, so it is strong but not fully prescriptive.

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