Look up a Nigerian postcode

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

Annotations already declare readOnlyHint, openWorldHint and idempotentHint, so the safety profile is covered. The description adds that output depth scales with level, which is useful, but the credit-consumption behavior for levels 2+ lives only in the schema, not the description.

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 compact sentence with no filler, and the primary behavior (confirm assignment) is front-loaded ahead of the secondary tiered behavior. Efficient, though it leaves room that could have been spent on sibling routing.

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-value explanation is unnecessary, and the parameter set is tiny. However, for a tool in a dense family of five similar postcode tools, the absence of any differentiation or usage context leaves the definition only minimally complete.

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%: the schema fully documents both postcode format and the five level tiers including credit cost. The description adds no syntax, format or default detail beyond what the schema already provides, so the baseline 3 applies.

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+resource: confirming a postcode is assigned and returning address details at higher levels. It is clear what the tool does, but it does not explicitly distinguish itself from the sibling validate_postcode, which plausibly covers the same 'is it assigned' check.

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?

The description offers no when-to-use or when-not guidance and never names an alternative, despite four closely related siblings (validate_postcode, autocomplete_postcode, find_postcode_at_location, resolve_address). The only routing signal ('at higher levels') refers to the level parameter, which the schema already explains.

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