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

With readOnlyHint and openWorldHint already declared, the description adds meaningful behavioral context: model input affects date availability, and the result is one of own_team, palletline_kerbside, or not_available. It does not describe error cases or exact response shape, but it is substantially more informative than the annotations alone.

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 is three compact sentences, front-loaded with the core question, followed by parameter guidance and return outcomes. Every sentence contributes useful information without repetition.

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?

Given the simple two-parameter schema, read-only annotations, and no output schema, the description provides enough context to call the tool correctly. It covers purpose, the model parameter's effect, and the possible return categories.

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 by explaining why the optional model parameter should be passed: it yields dates that account for the item's stock. Postcode semantics are already covered by the schema, but the model behavior is a useful addition.

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 states a specific verb-resource pair: checking UK postcode delivery availability, method, and dates. It also names the return outcomes, so an agent can distinguish this from product, basket, and enquiry siblings without opening the schema.

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 clearly establishes the context: use it to determine whether delivery is possible and which dates/methods are available. It adds the useful condition that passing a model enables stock-aware dates, though it does not explicitly state exclusions or a sibling alternative.

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