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

Annotations already cover the safety profile (readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false), so the description's job is added context. It contributes two useful facts beyond the annotations: the message reaches an external human, and a reply arrives within one business day. It does not mention that repeated calls could generate duplicate enquiries despite non-idempotency, which would have been worth stating.

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?

Three short sentences, zero filler, with the action statement front-loaded and the usage constraint immediately after. The response-expectation sentence is short and earns its place by setting the user's expectation.

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 four-parameter outbound message tool with fully documented params, no nested objects, and no output schema, the description covers action, consent gating, and turnaround. The only meaningful omission is that it never warns the agent that a second call creates a second enquiry, which matters given idempotentHint=false.

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%, so all four parameters (name, email, company, message) are already documented in the schema. The description adds no syntax, format, or content guidance for any parameter, so the baseline of 3 is appropriate.

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 and resource ('Send an enquiry to National Digital') and adds the acting-on-behalf-of framing, which tells the agent this is an outbound communication on a user's behalf rather than a data lookup. It does not explicitly contrast itself with the siblings (estimate_project, fetch, get_pricing_and_services, search), but the action is distinct enough that confusion is unlikely.

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?

Gives an explicit gating condition: 'Only use this when they have asked you to make contact.' That is both a when-to-use and a when-not-to-use statement, which is exactly what an agent needs before firing off an outbound message. No alternative tool is named because none of the siblings is a substitute for this action.

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