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

The readOnlyHint annotation already declares this is a safe read operation. The description adds that it returns a URL, but no deeper behavior (e.g., whether it returns multiple results, if the postcode must be formatted a certain way). Given the annotation, this is adequate but not rich.

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?

A single, front-loaded sentence with no redundancy. It conveys the essential action and input with maximum efficiency.

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?

The tool is simple (one required parameter, read-only, output schema present). The description fully covers what the tool does and the input needed. With an output schema, no return-value details are necessary. It is complete for the given 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 has 0% description coverage, so the description must clarify the parameter. It does state 'for a postcode', which tells the agent the parameter is a postcode string. However, it does not specify expected format (e.g., with/without space, case) or any validation rules, leaving some gap.

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 uses a specific verb ('Find') and resource ('council planning portal URL') with a clear parameter ('for a postcode'). It distinguishes from siblings like prop_epc_certificate or prop_ppd_transactions by specifying the exact output.

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 clearly implies when to use: whenever a council planning portal URL is needed for a postcode. It provides context but does not explicitly mention alternatives or exclusions, yet the purpose is narrow enough that no ambiguity exists.

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