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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful operational context that annotations cannot: the Metropolitan Police has ~680 neighbourhoods so results should be name-filtered, which is a result-size/performance caveat 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?

Three dense sentences, each earning its place: what it decodes, when to use it, and the large-result caveat plus alternative routing. The most important framing (this is the vocabulary/decoder tool) is front-loaded.

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 an output schema present, the description needn't explain return shapes, and it covers everything else an agent needs: trigger conditions, topic meanings, the sibling alternative, and the Met Police filtering caveat. Nothing required to call it correctly is missing.

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 force/month/topic/name_contains semantics, patterns and cross-topic constraints are already fully documented in the schema. The description's mentions of name_contains and force-required-for-neighbourhoods largely restate that, so the baseline 3 is appropriate for a schema that 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 action (decode/lookup reference data) and enumerates the four resource types it returns (force ids, category slugs, neighbourhood ids, availability), which maps cleanly onto the topic enum. It also explicitly distinguishes itself from ukcrime_find_neighbourhood, so an agent can route without opening either schema.

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?

'Use it when a force, category, neighbourhood id or month is unknown' gives the precise trigger condition, and the closing sentence names the alternative tool and the exact scenario (lat/long to force/neighbourhood) that should select it instead. Both the when-to-use and when-to-use-something-else conditions are explicit.

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