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

Annotations already indicate this is not read-only. The description adds valuable behavior beyond that: segments are live and always reflect current contacts, and the return shape is specified. This enriches the agent's understanding without contradicting annotations.

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 three compact sentences. The primary purpose is front-loaded, followed by a key behavioral trait and the return structure. Every sentence carries essential information with no 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 a tool with a nested filter object and no output schema, the description covers the essential aspects: the resource, the filter composition, the live evaluation behavior, and the return format. It is complete enough for an agent to invoke the tool correctly.

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 50% (name lacks a description, filter has one). The description provides a high-level summary of filter types, but the schema already details each filter field (tags, country, custom_field, dates). The description does not elaborate on the 'name' parameter, which is left self-explanatory. It adds marginal value over the schema but does not fully compensate for the coverage gap.

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 states a specific verb ('Create'), a resource ('named reusable segment'), and the exact composition of filters (tags + country + custom field + signup date range). It also clarifies the segment is live and returns a specific structure, distinguishing it clearly from siblings like list_segments.

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 purpose is so clearly defined that an agent can infer when to use this tool (to create a reusable segment). However, it does not explicitly mention alternatives or exclusion conditions (e.g., 'use list_segments to view existing segments'), leaving the decision to inference.

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