lookup-postcodes

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It effectively describes key behaviors: the tool returns a structured result with center and postcodes data, requires a local database built from specific CSVs, and has default values for 'limit' and 'includeSelf'. It covers output format, prerequisites, and some defaults, though it lacks details on error handling, rate limits, or performance characteristics.

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?

The description is appropriately sized and front-loaded, starting with the core purpose. Every sentence adds value: the first explains the tool's function, the second details input requirements and optional parameters, the third describes the return structure, and the fourth covers prerequisites. There is no redundant information, and the structure flows logically from purpose to usage to output to setup.

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 the complexity (7 parameters, no annotations, no output schema), the description is mostly complete. It covers purpose, input semantics, output format, and prerequisites. However, it lacks explicit error scenarios (e.g., invalid postcodes or coordinates) and does not mention the sibling tool 'search-property-prices' for contextual differentiation, which could enhance completeness for an AI agent.

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?

The schema description coverage is 0%, so the description must compensate. It adds significant meaning beyond the schema: it explains that 'postcode' or both 'easting' and 'northing' are needed as the center, describes 'radiusMeters' as in meters, specifies default values for 'limit' (10) and 'includeSelf' (false), and clarifies 'adminDistrict' as a filter. This covers all 7 parameters with practical usage context, fully compensating for the lack of schema descriptions.

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 clearly states the tool's purpose: 'Look up UK postcodes (Code-Point Open) and find nearest neighbours using OSGB36 eastings/northings.' It specifies the verb ('look up' and 'find nearest neighbours'), the resource ('UK postcodes'), and the coordinate system ('OSGB36 eastings/northings'), distinguishing it from the sibling tool 'search-property-prices' which deals with property prices rather than postcode geolocation.

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?

The description provides clear context on when to use this tool: to look up UK postcodes and find nearest neighbours based on coordinates. It specifies input requirements ('Provide either `postcode` or both `easting` and `northing` as the center') and optional parameters for filtering. However, it does not explicitly state when not to use it or compare it to alternatives like the sibling tool, which might be relevant for some use cases.

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