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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, covering the safety profile. The description adds behavioral context beyond annotations: it specifies the data categories returned (active, trialing, past-due, canceled counts, MRR, ARR) and the operational prerequisite that Stripe must be connected. This is useful non-obvious context, though it does not describe error behavior or response shape.

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, no filler. The first sentence front-loads the tool's function with concrete metrics; the second gives usage guidance and the prerequisite. Every word earns its place.

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 single-parameter, read-only stats tool with annotations covering safety, the description is largely complete: it says what it returns, when to use it (with get_stripe_metrics), and its connection requirement. It does not describe a response schema (none exists) or granular details like time range or currency, but those are not essential for correct invocation.

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 schema covers the only parameter, companyId, at 100% with a clear description in the input schema. The tool description itself adds no additional parameter semantics, so with full schema coverage 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 verb ('Get'), a specific resource ('subscription statistics from Stripe'), and enumerates the exact metrics returned (active, trialing, past-due, canceled counts, MRR, ARR). It also distinguishes itself from the sibling get_stripe_metrics by describing a complementary role, so an agent can select it correctly.

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 usage context: it tells the agent to use this tool alongside get_stripe_metrics for a full revenue picture, and states the prerequisite that Stripe must be connected. It does not enumerate explicit when-not-to-use cases, but for a read-only stats tool, naming the complementary sibling is sufficient direction.

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