Autocomplete a Nigerian postcode

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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so safety and repeatability are covered. The description adds essentially nothing beyond the title and annotations — no mention of how many suggestions are returned, ordering, or behavior on non-matching prefixes.

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?

A single front-loaded sentence with no filler; every word contributes to the meaning.

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?

An output schema exists so return values need not be described, and annotations cover the safety profile. What is missing is sibling routing and any sense of result shape or matching behavior, leaving this roughly minimal for an autocomplete tool.

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?

With one parameter at 100% schema coverage, the schema already documents 'partial' including an example format ('EK 01 A'). The description references the partial-code concept but adds no format or matching semantics beyond the schema, so it sits at the baseline.

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 ('suggest completions') and resource ('postcode') with the scope of a partial input. It is clearly distinguishable from validate_postcode and lookup_postcode in broad terms, but never names or contrasts with those siblings explicitly.

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?

'Partly typed postcode' is an implied trigger condition, so an agent can infer this is for in-progress input rather than a complete code. However, no alternatives or exclusions are given (e.g., use lookup_postcode once the code is complete), leaving the routing decision to inference.

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