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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), so the description adds the genuinely useful extras: data source, geographic and temporal coverage limits, and that access is free. It omits pagination behavior and the default limit of 50, which matters for a list tool returning potentially large result sets.

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?

Roughly 60 words in a single front-loaded block: what the dataset is, its fields, coverage, filters, matching behavior, cost. The telegraphic field-list style is dense but every clause carries information, with no filler.

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?

Return values are covered by the output schema and coverage limits are stated, so the essentials are present. What is missing is behavior when no filters are supplied (all appeals nationwide? an error?) and the default page size, which an agent needs to call this correctly given zero required parameters.

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% across 7 parameters, so the description has to carry parameter meaning. It does partially: it identifies the decision filter, specifies ISO date format for the date filters, and implies location/lpa_code/postcode are authority-matching inputs. It never explains limit, the interaction or precedence between the three location parameters, or that all parameters are optional.

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 names a specific resource set (Planning Inspectorate appeal decisions) and enumerates the returned fields (case reference, council application reference, appeal type/procedure, site address, development type, decision, date), so an agent can distinguish it from planning_applications or planning_precedents. It does not explicitly name those siblings, so differentiation still requires inference.

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?

Scope conditions are stated (England only, decided from October 2021, matched to an authority, free), which implies when the tool applies. There is no explicit statement of when not to use it or which sibling to use for site-boundary matching beyond the oblique note that boundary matching 'comes with the national planning register'.

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