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

Annotations already declare read-only, idempotent, non-destructive, and closed-world behavior, so the bar is lower. The description adds meaningful domain context beyond annotations, including conditional outcomes (free insured pack in the Republic vs. own tracked post to Dublin from Northern Ireland) and details like return postage deduction waivers.

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?

The description front-loads the core purpose ('How the free insured postal pack works') and then enumerates covered topics efficiently. The first sentence is dense with a long list, but every item appears relevant and the second sentence cleanly covers the optional county parameter.

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 read-only information tool with no output schema, the description sufficiently explains what content the tool returns: request process, transit coverage, free-return terms, offer validity, deduction rules, and county-specific variations. It could be slightly more explicit about the default response when no county is given, but overall the agent has enough to invoke 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 coverage is 100%, so the baseline is 3, but the description adds real meaning about the county parameter: it yields that county's specific arrangement and illustrates the variation between Republic and Northern Ireland. That goes beyond the schema's neutral 'adds that county's postal arrangement and page.'

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?

The description clearly identifies the tool as returning explanatory information about the free insured postal pack, listing specific covered topics (transit coverage, return terms, validity, deductions, payment/ID). It distinguishes the resource well but does not explicitly contrast itself with the action-oriented sibling request_postal_pack.

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?

Usage is implied: an agent can infer to call this when users ask how the postal pack works or about a county's arrangement. The description gives guidance on when to supply the county parameter but never states when not to use this tool or names request_postal_pack as the alternative for actually requesting a pack.

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