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

Annotations already mark the tool as readOnly, idempotent, and non-destructive. The description adds meaningful behavior beyond this: blank pages return an error rather than a guess, and the return structure is disclosed with fields null when absent. This is solid transparency, though it omits details like rate limits or authentication requirements.

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?

The description is compact and front-loaded with the core purpose, followed by a key error behavior and a clear return structure. Every sentence earns its place, and there is no filler.

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?

Since there is no output schema, the description correctly and sufficiently documents the return keys and null behavior. It also covers the main error case. It is nearly complete for a low-complexity read-only tool, though it could better route agents away from sibling document tools.

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 100%, so the schema already documents both parameters. The description adds that doc_type selects the field schema, which clarifies its role. However, the description lists only six doc_type options while the schema lists additional valid types such as business_card, w2, and pay_stub, which could mislead an agent relying solely on the 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?

The description clearly states the tool's function: turning a document image into structured fields, with doc_type selecting the schema. It is specific about the resource and output, though it does not explicitly differentiate it from sibling tools like document_to_markdown or document_tables.

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 implies when the tool should be used: when structured field extraction from a document image is needed. It also gives a useful error condition for unreadable pages. However, it does not explicitly state when to prefer this over document_query, document_tables, or document_to_markdown, nor provide exclusions.

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