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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior. The description adds meaningful traits: last 12 published months, district-level aggregation, returned citation/attribution, and a conditional free_report_url for full postcodes, though it does not cover invalid-input or error behavior.

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-loads the resource and scope, then describes return contents, then the conditional free_report_url. Each sentence earns its place and the description is compact for the amount of behavior it discloses.

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 one-parameter read-only tool with full schema coverage and an output schema, the description supplies the key scope and conditional behavior an agent needs to call it correctly. No major contextual gap remains.

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 100%, so the baseline is 3. The description adds interpretation rules beyond the schema: a full postcode such as 'E8 1AA' is answered as its district 'E8', never as the exact postcode.

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 ('published street-crime figures') and scope ('postcode district'), and explicitly distinguishes the exact postcode case by saying it answers 'never for the exact postcode'. This clearly separates it from the exact-postcode-oriented sibling postcode_summary.

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?

Explains the input condition and aggregation rule, so an agent knows to use this for district-level crime figures rather than exact-address lookup. It does not explicitly name a sibling alternative or give broader when-not-to-use guidance beyond the exact-postcode distinction.

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