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

With no annotations, the description carries the full burden, and it does disclose the billing cost of 1 credit plus the full output surface. It says nothing about invalid/malformed postcode handling, UK-only scope (only implied via LSOA/MSOA/ONS), or whether results are cached — real gaps for a lookup tool with zero annotation coverage.

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?

One compact, front-loaded line with the output list first and the cost tag last — nothing wasted. The verbless fragment style is terse but readable and does not obscure meaning.

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 single-parameter lookup with no output schema, the enumerated return fields substitute well for a missing output schema. Only the absence of error/scope behavior keeps it from being fully complete.

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?

Coverage is nominally 100%, but the schema text for the sole parameter is the placeholder 'string, required', so it conveys almost nothing. The description only reinforces that the argument is a postcode; it adds no format guidance (spacing, casing, partial postcodes).

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 description names the input resource (postcode) and enumerates the derived outputs (coordinates, region, local authority, ward, constituency, LSOA/MSOA, ONS codes), so the agent knows exactly what comes back. It stops short of distinguishing itself from the sibling 'geocode' tool, which plausibly overlaps on the coordinates portion.

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?

There is no explicit when-to-use statement, no exclusions, and no pointer to an alternative such as 'geocode' for address-level lookups or 'ons_search' for area statistics. Usage is only inferable from the tool name and the output list.

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