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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world. The description adds value beyond them: geographic coverage limit ('UK only'), cost ('Free'), and the crucial behavioral fact that the returned portals are not machine-readable, which sets expectations for the output. It does not contradict anything.

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?

Three short sentences, front-loaded with the identity of the resource and immediately followed by the scope caveat and input rules. Every sentence carries information; nothing is 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?

An output schema exists, so return values need not be re-explained, and the description nonetheless summarizes them (authority + portal URL). Combined with the format and coverage notes, an agent has what it needs, though edge-case behavior (missing/invalid inputs, non-UK postcodes) is left unspecified.

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 description coverage is 0%, so the description must carry the load, and it does: it tells the agent the two parameters are alternatives ('either postcode or location') and gives the required format for location ('lat,lng'). It omits what happens if neither or both are supplied, so it is not exhaustive.

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?

States a specific resource (the local planning authority for a location plus its portal URL) and explicitly scopes what it returns versus what it does not ('WHERE to look, not the applications themselves'). This cleanly separates it from siblings like planning_check, planning_designations, and property_planning_history.

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 line 'council portals are not machine-readable' hints at why you'd use this (to get a link rather than data), and 'UK only' bounds applicability, but no sibling is named and there is no explicit when-to-use/when-not guidance versus planning_check or planning_precedents. Usage is implied rather than stated.

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