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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered; the description usefully adds the return format and column set. However, it leaves a real ambiguity: it accepts page/limit (max 100), so it is unclear whether the CSV covers all matching contacts or only one page, and no note on result size or rate limits is given.

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?

One front-loaded sentence that names the action, the filter scoping, the output format, and the columns. Nothing is wasted and no sentence is buried.

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 12 parameters, 92% schema coverage, and full annotations, the definition is serviceable but thin: the pagination behavior of an export, and how it differs from list-contacts, are left unstated. Since there is no output schema, a short note on the CSV's shape/paging would have closed the gap.

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 92%, so the baseline is 3; the description does add a bit by framing the parameters as filters that shape the exported column set (email, names, subscription, audiences, custom fields). It does not add syntax or semantics for individual parameters, which the schema already handles well.

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 ("Export contacts") plus the output form (",CSV text") and the columns produced, which is more informative than the title alone. It stops short of naming the closest sibling (list-contacts) to make the export-vs-list distinction explicit, so it is clear but not fully differentiated.

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?

"matching the filters" and "as CSV text" imply the use case (get a CSV of a filtered contact set), but there is no explicit when-to-use, when-not-to-use, or alternative such as list-contacts. Guidance is inferred from format rather than stated.

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