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

Annotations already declare readOnlyHint, openWorldHint, and destructiveHint, so the safety profile is covered. The description adds useful behavioral context by saying it returns criteria, status, and matched-account count, and by explaining that lookback_window affects counting. It does not cover error cases or id/name precedence, which keeps it below 5.

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 sentences, front-loaded with the action and resource, with zero wasted text. The lookback_window detail is placed where it is useful without bloating the description.

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?

With no output schema, the description appropriately states what is returned: criteria, status, and match count. It is nearly complete for a simple read tool, but it does not clarify behavior when both segment_id and segment_name are supplied, or when neither is supplied despite no required parameters.

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 parameters are already well documented. The description reinforces lookup 'by id or name' and explains that lookback_window should match the audience window, but adds little beyond the schema's existing parameter descriptions. Baseline 3 is appropriate.

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: 'Read one saved Insights segment.' It also specifies the return contents (criteria, status, match count) and supports lookup by id or name, which distinguishes it from list_segments and create_segment without needing to inspect 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?

It clearly frames the tool as a single-segment retrieval operation and mentions passing lookback_window when counting within an audience window. It does not explicitly name alternatives such as list_segments or state exclusions, so it falls short of a 5.

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