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

With no annotations, the description must carry the behavioral load: it does disclose that invalid ids are rejected and that a checkout-issued id is mandatory, which is genuinely useful. However it never states the auth/API-key requirement, whether the call is read-only, or what error vs. success looks like, so coverage is partial for an unannotated tool.

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?

Three short sentences, zero filler, with the core action front-loaded and the prerequisite immediately after. Every sentence contributes new information.

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 lookup this is close to sufficient: it names the input contract, the validation behavior, and the backing endpoint. The remaining gap is the absence of any indication of what the status response contains, which matters since there is no output schema.

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% with a single well-documented parameter including a regex pattern, so the schema already does the heavy lifting. The description adds only provenance ('from checkout') and format ('sub_…'), which is marginal beyond the schema's own pattern and description.

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 (check) and resource (Pro subscription status) plus the exact identifier type (Stripe sub_ id). This is clearly distinct from the sibling tools (site info, unlock-from-session, numbers-to-Excel), so an agent can route to it without ambiguity.

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?

Establishes the precondition that a real sub_ id from checkout is required and that invalid ids are rejected, and references GET /api/pro-status as the equivalent path. It lacks explicit 'when not to use this / use X instead' guidance, which is the only gap.

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