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

Beyond the annotations, the description discloses that the check is offline, exactly what it validates (required fields, postcode range, province consistency), what it returns (normalised fields plus problem messages), and a key limitation (does not confirm street or person existence). This is rich behavioral context that an agent would otherwise have to discover.

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 front-loaded with when to use, then moves through what is checked, what is returned, and the key exclusions. Every sentence adds value with no wasted words.

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?

No output schema exists, but the description explains the return shape (normalised fields + problem list). It covers validation rules, limitations, and exclusions, so an agent has everything needed to call it correctly without guessing.

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. The description adds meaning by clarifying which fields are required for delivery, the postcode range (01000–52999), and the province–postcode matching rule—details not present in the schema.

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 (check) and resource (Spanish postal address), and explicitly situates it before creating a burofax. An agent can tell exactly what this tool does and how it fits with the sibling create_burofax_draft.

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 gives clear when-to-use (user provides a Spanish address, before creating a burofax) and an explicit exclusion (do not use for addresses outside Spain). It does not name the alternative sibling (create_burofax_draft) by name, but the workflow context is strong enough to route correctly.

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