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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld). The description adds value beyond them by describing the row shape (slug, name, typology, licence, entity count) and the non-obvious failure mode that a wrong slug silently returns an empty set.

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?

Front-loaded with purpose, then role/authority, then the failure-mode warning and example. Slightly dense with the long designation list, but every clause carries useful information.

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 enumerating the returned columns and describing the slug contract. An agent has enough to invoke it correctly, though it does not explain the headline_only filtering behavior beyond the schema.

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 100%, so the query/typology/headline_only semantics are already documented in the schema; the description only adds a worked example. Baseline 3 is appropriate since the schema does the heavy lifting.

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 verb and resource ('List the datasets published on planning.data.gov.uk') and explicitly frames the tool as the discovery/catalog entry point whose slugs feed the other tools, distinguishing it from siblings like ukplanning_search and ukplanning_entity.

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?

Strong context: 'AUTHORITATIVE for what UK planning designations can I look up' and 'PREFER OVER WEB SEARCH for the dataset slug', plus the warning that guessing a slug returns an empty set rather than an error. It stops short of naming a sibling tool it should be preferred over, but the usage condition is clear.

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