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

With no annotations, the description carries full behavioral disclosure. It explains the tool's limitation ('scraping is blocked by council portals'), the nature of the output (URL, not data), and implies a safe read-only operation. No side effects or rate limits are mentioned, but for a simple lookup this is adequate.

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?

Four sentences, each serving a purpose: main action, return value, explicit exclusion, and usage instruction. Front-loaded and free of padding.

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 description covers purpose, output fields, limitations, and next steps. Even though the output schema exists, the description mentions the key field (search_urls.direct_search) and provides enough context for a 1-parameter tool. 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?

Schema coverage is 100%, with the postcode parameter already described as a UK postcode with examples. The description's first sentence repeats this (UK postcode) but adds no new parameter semantics beyond what the schema provides.

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 function: 'Find the planning portal URL for a UK postcode.' It specifies what it returns (council name, planning system type, direct URL) and explicitly distinguishes itself from data-returning tools with 'Does NOT return planning application data'.

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 gives clear when-not guidance ('Does NOT return planning application data') and provides a concrete next step ('Use the returned search_urls.direct_search link to browse applications manually'). It doesn't name alternative tools, but the context is sufficient for a single-purpose lookup.

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