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

Annotations already provide readOnlyHint=true, and the description adds meaningful behavioral nuance: it counts only the current shared agent when operating a shared agent, and it clarifies that 'No match' people are already in classified_people. This goes beyond the annotation without contradicting it.

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 well-structured with a <summary> and <returns> section, front-loading the core meaning. Every sentence adds value—scope, relationship to classified_people, shared-agent behavior, and the 'No match' distinction—without redundancy or fluff.

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 one-parameter read-only tool, the description is complete: it explains the counting scope, clarifies edge cases, names related tools, and explicitly describes the return dictionary {group_id, unclassified_people}. Since no output schema exists, the return description fills that gap adequately.

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% and the single required parameter group_id is already described as 'The segment group to count for (from list_segment_groups).' The description adds the concept of 'classify scope' and mentions the return fields, but it does not materially enrich the parameter semantics beyond what the schema provides, so the baseline of 3 applies.

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 action ('get') and resource ('segment unclassified count') and defines exactly what is counted: people in the group's classify scope with no classification row yet. It also distinguishes the concept from 'No match' people and links it to the 'classified_people' count from list_segment_groups, so an agent can clearly understand the tool's unique purpose.

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 provides clear context for when this tool is relevant: it pairs with the classified count from list_segment_groups and represents the population that a classify_segment_group run with force off would process. It does not explicitly say 'use this instead of X' but the relationship to sibling tools is sufficiently clear.

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