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

Although annotations already cover read-only/idempotent safety, the description adds substantial behavior beyond them: failed/unreadable results stay unknown, no clear-site or statutory-completeness claim, freshness and red-line intersections unverified, non-UK returns a coverage error, all-unresolved returns CONSTRAINT_EVIDENCE_UNAVAILABLE, and a regional ground lookup is not a full-radius screen. That is exactly the kind of epistemic-limit disclosure an agent needs.

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 the verb and scope, then caveats, then chaining. The long constraint enumeration is dense but each item is scope-defining. Slightly run-on in the caveat sentences, but no filler sentences.

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?

For a 4-param, nested-object, high-stakes lookup tool with an output schema, the description covers scope, limits, error semantics, and chaining. An agent could call it correctly and interpret ambiguous results without further context.

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 only 50%, but the description compensates well: it explains that include[] restricts to specific constraint types (and lists them), addresses the UK-only behavior of address, and gives detailed chaining semantics for site_ref including what gets reused. radius_meters is never explained in the description despite the 'full-radius screen' hint, leaving one parameter ambiguous.

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 ('Check first-pass UK planning constraints at a site') and enumerates the exact constraint categories covered, letting an agent distinguish it from siblings like get_flood_risk or prepare_heritage_review. The UK-only scope is stated up front.

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?

Explicit sequencing guidance is given: 'Use after analyze_site when per-constraint detail is needed,' plus UK-only behavior and the include[] narrowing option. It does not explicitly say when to prefer get_flood_risk or prepare_heritage_review instead, so the alternative-routing is only partial.

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