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

Annotations only declare readOnlyHint=true, so the description carries the interesting behavior: on a shared agent it counts only the current shared agent, and it clarifies that 'No match' people are excluded from this remainder. That is genuine context beyond the safety hint, though it says nothing about cost, latency, or freshness of the count.

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 core answer is front-loaded in the first clause, and the summary tag keeps supporting detail (shared agent, No match distinction) contained. The XML tag scaffolding and the separate returns block make it slightly heavier than needed, but no sentence is padding.

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?

Although there is no output schema, the <returns> block gives the exact return shape ({group_id, unclassified_people}), and the summary covers scope, shared-agent behavior, and the neighbor metric it should be paired with. Nothing an agent needs to call and interpret this correctly is missing.

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 100% and both parameters (`group_id`, `on_behalf_of`) are fully documented in the schema, so the schema does the heavy lifting. The description's reference to `criteria` and the shared-agent scoping adds a little framing but no syntax or format detail beyond what the schema already provides. Baseline 3.

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?

States a precise verb+resource ('how many people ... have no classification row yet') and scopes it to the group's classify criteria. It also explicitly distinguishes this count from the 'No match' people, who are already inside `classified_people`, which is exactly the confusion an agent would otherwise hit.

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?

Gives clear context for when this is the right number: it is the population a `classify_segment_group` run with force off would process, and it pairs with `classified_people` from `list_segment_groups`. It does not name an explicit alternative tool to use instead, so it stops short of full when/when-not routing.

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