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

Annotations only declare readOnlyHint and openWorldHint; the description adds real behavioral context the agent could not otherwise know — no point cost, single-result output, attribution/licensing obligations, and a privacy_consent_required failure mode with an explicit instruction not to fabricate consent. The licensing date and per-country ODbL remarks are mildly noisy but do convey compliance obligations.

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?

Roughly six short sentences for a two-parameter lookup; the useful facts (points, URL, privacy consent) are there, but the licensing aside ('read on 2026-11-08', 'Some countries name ODbL') dilutes the front-loaded purpose and pushes operational guidance later.

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 simple two-param read-only lookup with no output schema, the description covers cost, cardinality, and the consent error path, which is more than most. It is still incomplete on parameter formats and on what the single result contains, which are the two things an agent most needs to call it correctly.

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 0% and both required parameters (country, code) are undocumented. The description adds only an oblique hint that 'code' is not a URL; it never states that country must be a two-letter uppercase ISO code or what 'code' looks like, so it fails to compensate for the schema gap.

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?

Identifies a specific verb+resource ('postal lookup at PostalCodes.info') and marks itself as the second/backup option versus the sibling hub_postal, plus clarifies output cardinality ('One result is returned, not a database dump'). It never actually says what a lookup yields (place name, region, coordinates), so the resource is clear but the result is not.

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?

'A second postal lookup' implies fallback usage after hub_postal, but the description never states the selection condition explicitly (e.g. 'use when hub_postal returns no match'). The 'does not accept a URL' and 'does not spend points' remarks hint at alternatives without naming them.

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