lookup_postcode

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

No annotations provided, so the description carries full burden. It implies a read-only lookup by listing returned data, but does not explicitly state it is non-destructive, mention authentication, rate limits, or other behaviors.

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 a single paragraph that front-loads the main purpose, but it lists many data categories, making it slightly verbose. Every sentence adds value, but could be more concise.

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?

With no output schema, the description compensates by listing all categories of returned data, providing sufficient context for an agent to understand the output. It also notes the unsupported region, making it complete for its complexity.

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 coverage is 100% with a description and example for the only parameter 'postcode'. The description adds no new semantic meaning beyond the schema's explanation.

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 states 'Look up enriched data for a UK postcode' and lists specific data categories (geographic, risk, property, broadband, deprivation, MP details), clearly distinguishing it from siblings like 'nearest_postcode' and 'postcodes_within'.

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 explicitly states it is for UK postcodes and notes that Northern Ireland (BT prefix) postcodes are not supported, providing a clear when-not-to-use condition. It does not name alternative tools but the sibling names imply different purposes.

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