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

With no annotations, the description does carry some behavioral weight: it discloses the paid/complete-session precondition, that invalid ids are rejected, and that the logic mirrors GET /api/unlock. It does not say whether resolving has side effects (e.g. writing a local entitlement record), what auth is needed, or what the payload contains.

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, front-loaded with the verb and resource, then constraints. No filler and nothing repeated from the schema.

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 one-parameter tool with no annotations and no output schema, the description covers purpose, precondition, failure behavior, and hints at the return value ('local entitlement payload'). Only side effects and auth requirements are left unstated.

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%, so the baseline is 3; the description earns an extra point by adding validation semantics the schema cannot express — the session must be paid/complete and invalid ids are rejected. Format/prefix details remain the schema's job.

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: resolve a Stripe Checkout session_id into a local entitlement payload, and even names the equivalent REST endpoint. It does not explicitly contrast with the nearest sibling (get_pro_status), so it stops short of full 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?

'Requires a paid/complete session' is a precondition rather than a when-to-use rule, and nothing tells the agent when to prefer this over get_pro_status for entitlement lookups. Usage is implied by the input (you have a cs_… id) but not routed.

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