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

Annotations already provide readOnlyHint, idempotentHint, and destructiveHint, so the description's burden is lighter. It adds valuable behavioral context not captured by annotations: the result is advisory and requires human review, the tool costs 0.25 USDC per accepted request, and it requires an owner-authorized x402-capable client. No contradiction with annotations exists.

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?

Four sentences, each earning its place: the core function, the intended use case, the advisory/cost/auth constraints, and a pointer to the free sibling tool. The most important information is front-loaded, and there is no filler or repetition of schema details.

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?

Given that an output schema exists, the description does not need to explain return values. It covers when to use the tool, prerequisites, cost, human-review requirements, and the alternative tool. For a read-only analysis tool with rich schema and annotations, the description is complete enough for an agent to decide and invoke correctly.

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%, so the description must compensate. It does convey that `input` can be receipt text or a provider-neutral structured extraction, and 'duplicate detection' hints at the role of `existing_fingerprints`. However, it does not explain the `contract_version` parameter or the SHA-256 fingerprint format, leaving some required parameters only implied.

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 uses a specific verb and resource: 'Extract and validate structured expense data from receipt text or a provider-neutral receipt extraction.' It lists the domain (expense data), the processing (extraction, validation, duplicate detection, arithmetic checks), and distinguishes itself from the sibling by directing users to get_receipt_example for a fixed free example.

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 explicitly states when to use the tool: 'Use when an agent needs merchant, date, tax, total, line items, confidence, duplicate detection, and arithmetic validation before creating or reconciling an expense.' It also specifies prerequisites (owner-authorized x402-capable client), cost, and names the alternative get_receipt_example for a free example.

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