Preview contacts matching conditions

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

Annotations already declare readOnlyHint=true and destructiveHint=false; the description reinforces this by saying 'Nothing is stored and no contact is modified.' It also adds useful context about the condition body being shared with segment creation/update, which clarifies what the tool does with the request. This goes beyond the annotations without contradicting them.

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 tight and front-loaded: the first sentence states the core purpose, the second adds the preview-vs-persist distinction and non-destructive behavior, and the third gives a necessary prerequisite. Every sentence earns its place and there is no redundant or filler content.

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?

The description covers the main behavioral contract: previewing, not persisting, no modifications, and checking both who and how many. It also references the prerequisite filter attributes endpoint. With no output schema, it could more explicitly describe the response shape, but 'check who a filter reaches, and how many' conveys the essential return semantics.

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 the baseline is 3, but the description adds context about the conditions parameter: the body is the same accepted when creating or updating a segment, and it directs callers to the segment filter attributes endpoint for valid attribute/operator/value combinations. This helps an agent understand the semantics of the nested conditions parameter beyond the raw 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 opens with a specific verb and resource, 'Preview the contacts matching a set of conditions,' and immediately distinguishes the tool from segment persistence with 'without saving a segment.' It also states that the body is the same conditions accepted when creating or updating a segment, which clearly separates it from sibling segment creation and listing tools.

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?

It clearly states when to use the tool: 'this is how to check who a filter reaches, and how many, before persisting it.' It also gives an explicit prerequisite, 'Call the segment filter attributes endpoint first,' which is useful operational guidance. It does not explicitly name alternative segment-creation tools or list when not to use them, but the pre-persistence framing is clear enough.

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