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

Annotations already declare readOnly, idempotent, closed-world and non-destructive, so the description only needs incremental context. It adds two genuinely new facts: the record is 'durable' (persistent, retrievable later) and the call requires the 'orders:read' scope — an auth prerequisite the annotations do not carry.

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, both earning their place: purpose first, then the scope requirement. No filler, no restatement of the title.

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 tool with full annotations and no output schema, the description covers what the tool returns conceptually, what it operates on, and the required auth scope. The remaining gap is the absence of any note on what happens when the purchase id is unknown or not a support purchase.

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 0% and the only parameter, purchase_id, is documented solely as a UUID format. The description ties it loosely to a 'completed voluntary support purchase', which is marginally useful, but never states that a non-support order id will fail or how to obtain the id.

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?

Specific verb ('Read') plus a precisely scoped resource ('durable receipt for a completed voluntary support purchase'). It implicitly separates itself from buy_agent_support (mutation) and from generic order readers like get_order, though it never names a sibling explicitly.

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 phrase 'completed voluntary support purchase' implies this is a post-purchase lookup, so usage is inferable. However, there is no explicit when-to-use guidance nor any pointer to alternatives such as get_order or get_credit_purchase when the agent has an order id rather than a support purchase id.

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