count_segment

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

With no annotations, the description carries the behavioral burden. It conveys that this is a read-only, current-state count and provides a practical reason for using it. However, it does not disclose return format, error behavior, or whether the count is computed in real time, leaving meaningful gaps.

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?

Two concise sentences, front-loaded with the core purpose and followed by a useful usage example. There is no wasted language or unnecessary repetition of schema details.

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 single-parameter read-only count tool, the description is largely complete: it states what is counted, when to use it, and implies the return is a count. It would benefit from explicitly confirming the response shape or behavior for invalid IDs, but those are minor for this complexity level.

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 0%, and the description adds no explicit meaning to the required 'id' parameter beyond referring to 'a segment.' The agent must infer that 'id' is the segment ID from the tool name and prose, which is only minimal compensation for the lack of schema documentation.

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 clearly states the tool counts how many contacts a segment currently matches, with a specific verb and resource. It does not explicitly differentiate itself from sibling tools like list_segments, but the meaning is unmistakable.

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 concrete usage context: run this before building a campaign to check whether a segment matches anyone. It does not mention when not to use it or point to alternatives, but the guidance provided is clear and actionable.

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