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

With no annotations, the description carries the full behavioral burden, and it discloses only the credit cost (3 credits), which is genuinely useful operational context. It says nothing about input constraints (file size, page limits, supported formats), latency, failure behavior, or what happens on an unreadable document.

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 short, front-loaded sentences with zero filler: purpose first, cost second. Every clause 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?

There is no output schema, so the return value is entirely on the description — yet it never indicates what structured fields are extracted or in what shape, which matters for a parsing tool. Cost and purpose are covered, but that gap plus absent input constraints keeps it only adequate.

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?

One required parameter with 100% schema description coverage, so the schema already explains document_url fully as a URL to a PDF/image. The description adds no syntax, size, or format guidance beyond that, which is the expected baseline when the schema does the work.

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 (extract) and resource (structured data from invoices and receipts), which an agent can clearly distinguish from generic siblings like documents or scrape. It stops short of naming an alternative or bounding scope, but the purpose itself is unambiguous.

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?

No when-to-use guidance, no conditions, no named alternatives. The only routing signal is implicit ('invoices and receipts'), so an agent must infer when this beats documents or scrape on its own.

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