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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety and scope are covered. The description adds the qualifier 'current,' hinting that the count is live rather than historical, but never clarifies freshness, whether it is exact or approximate, or what the return value looks like (there is no output schema).

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 short sentences with zero waste: purpose first, then the intended use case. Nothing is repeated and nothing is buried.

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 simple three-parameter read tool with full schema documentation and annotations covering safety, the description covers what is needed to call it correctly. The only real gap is the shape of the return value, since no output schema exists to state that the count is a plain number.

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%, with each of cohortId, projectId, and environment documented in the schema itself, so the baseline applies. The description adds no parameter-level meaning beyond what the schema already supplies.

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 specific verb and resource: 'Return the current member count for a player cohort.' That distinguishes it in spirit from get_cohort_members and get_cohort_membership, but the description never names those siblings, so the differentiation is implicit rather than explicit.

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?

'Use to size a cohort before sampling members or checking membership' gives a clear motivating context for calling it. It stops short of naming the alternatives (get_cohort_members, get_cohort_membership) or stating when not to use it.

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