Create a segment

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

Annotations already indicate readOnlyHint=false and destructiveHint=false, so the description's 'Creates' is consistent. It adds meaningful behavioral context by explaining the default evaluation timing (only on subscribe) and how add_segment_on_page_load changes it, plus the rule syntax. It does not cover edge cases like duplicate names, but the annotations cover the safety profile and the output schema covers response expectations.

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 compact: three sentences front-loaded with the core purpose, followed by criteria syntax, then the page-load behavior nuance, and a closing guardrail. Every sentence serves a distinct informational purpose 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?

Given the tool's complexity (nested objects, 4 params, output schema present), the description covers the essential behavioral aspects: what the tool does, the criteria rule format, the default and alternative evaluation behavior, and when to include optional fields. The output schema handles return-value descriptions, so no gap remains.

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 each parameter is already well-documented. The description adds usage-level guidance (when to include optional parameters) but does not enrich semantic meaning beyond what the schema provides. The rule syntax and defaults are reiterated, which is helpful but not additive to schema knowledge.

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 and resource ('Creates a new segment on the current site'), immediately distinguishing it from listing or updating tools. It clearly identifies the creation action and the resource type (segment), and the sibling context (e.g., list_segments) reinforces this distinction.

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 clear context on when to use this tool: when creating a segment, with optional criteria. It explicitly instructs 'Only include segment_criteria and add_segment_on_page_load when the user explicitly describes the matching rules,' which is a valuable guardrail. However, it does not explicitly name alternatives or conditions where another tool (e.g., create_audience_group) might be preferred, though the segment-specific scope is implicitly clear.

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