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

Annotations already declare readOnly=true, idempotent=true, destructive=false, so the safety profile is covered. The description adds real behavioral context: the return shape ('per business, whether it replied and the latest reply') and the hard precondition that refs must originate from send_message_to_vendor. It does not say whether results reflect live or cached reply state, which is a minor gap for a polling-style tool.

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 tight sentences loaded front-to-back: trigger condition, required input with provenance, expected output, then exclusions. Every clause earns its place with no restatement of the name or title.

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?

With no output schema, the description carries the return-value burden and does so ('per business, whether it replied and the latest reply'). Combined with annotations covering the safety profile and full schema coverage of the sole parameter, the definition is nearly self-sufficient; only freshness/caching of reply data is unstated.

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% and the single parameter is already documented, so the baseline is 3. The description goes further by specifying provenance ('Pass the enquiry_refs that send_message_to_vendor returned'), which tells the agent where valid values come from — meaningfully more than the schema's type/maxItems constraints.

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 (check whether a business replied to an enquiry) and anchors it to the producing sibling send_message_to_vendor. An agent can distinguish it from search_vendors/get_vendor without opening any 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?

Explicit when-to-use (user asks whether a business answered an enquiry sent earlier in this conversation) plus explicit when-not-to-use (enquiries sent outside this conversation or without a ref) and an anti-pattern warning ('never guess a ref'). Nothing is left to inference.

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