reach_previewContactsMatchingConditionsV1

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

With no annotations provided, the description carries the full burden and handles it well: 'Nothing is stored and no contact is modified' explicitly discloses the non-destructive, side-effect-free behavior, and it explains the shared conditions format with segment create/update plus the dependency on the filter attributes endpoint. The only gap is silence on pagination behavior and limits, which matters given page/per_page parameters.

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 paragraphs with the core purpose front-loaded in the first sentence. The second paragraph adds the shared-format and dry-run context, and the third adds the prerequisite workflow. Every sentence earns its place with no redundancy or filler.

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 an 8-parameter tool with no annotations and no output schema, the description covers the essential ground: purpose, the dry-run/safety profile, the shared conditions format, and the prerequisite discovery call. The phrase 'who a filter reaches, and how many' implies the response shape. Minor omissions are explicit return structure and pagination semantics, but page/per_page in the schema make this largely self-evident.

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 meaningful value on top: it states the conditions body is identical to what segment create/update accepts, giving cross-tool semantic context, and it points to the authoritative filter-attributes endpoint for valid combinations — supplementing the attribute and operator descriptions. This clear added value justifies a 4.

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 opening line uses a specific verb ('Preview') plus resource ('contacts matching a set of conditions') and a defining scope qualifier ('without saving a segment'). This clearly distinguishes it from segment-creation siblings like reach_createAProfileSegmentV1 and from contact-listing tools like reach_listContactsV1 — an agent can tell what this does 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 gives explicit when-to-use context: 'this is how to check who a filter reaches, and how many, before persisting it.' It also states a clear prerequisite workflow: call the segment filter attributes endpoint first to discover valid attribute/operator/value combinations. It stops short of naming alternatives or explicit when-not-to-use cases (e.g., counting contacts in an already-saved segment, which reach_countProfileSegmentContactsV1 handles), so it misses the top tier.

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