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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the bar is lower, yet the description still adds real behavioral semantics: the definition of Active (OrganizationMember.isActive true), the rule that billableSeats EXCLUDES agent personas, and the max-with-floor-of-1 computation. That is domain behavior an agent could not infer from annotations or the empty 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?

Front-loaded with the full field list, then two supporting sentences on the Active rule and the billableSeats exclusion; every clause carries information. The inline code citations ('CLAUDE.md note 79', 'routes/billing.ts') are more traceability than agent-facing guidance, a minor structural cost.

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?

There is no output schema, so the description carries the return-value burden and does so thoroughly by enumerating every reported figure and the semantics of the key one (billableSeats). Combined with annotations covering the safety profile and zero parameters, nothing an agent needs to call 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?

The tool takes zero parameters, so the baseline of 4 applies. The description correctly adds nothing about arguments, and the empty schema (additionalProperties false) is consistent with the description's account of a parameterless read.

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 ('Read') and resource ('caller org's seat-count breakdown') and then enumerates the exact fields returned, so an agent knows precisely what comes back. It never names a sibling or draws a boundary against look-alikes such as get_plan, get_plan_features, get_my_quota_usage or list_org_members, so it stops short of explicit sibling differentiation.

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?

Usage is only implied: the note that billableSeats is 'the figure Stripe meters on' and that it mirrors 'the real billing path' signals this is the tool to call for authoritative billing counts. There is no explicit when-to-use/when-not-to-use statement and no mention of alternatives for org-membership or plan questions.

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