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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses non-obvious behavior: the file is not stored, there is a rate limit of 5 per email per day, an email is required, and extracted values are treated as data rather than instructions (prompt-injection guard). These are exactly the traits annotations cannot convey.

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?

Front-loaded with purpose and payload, then constraints and safety notes in tight declarative sentences. Every clause carries information; nothing is padding.

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 description correctly enumerates the returned fields an agent would rely on, and it covers input constraints, rate limits, persistence, and safety. Nothing needed to invoke it correctly is missing.

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 a baseline of 3 applies. The description adds real meaning beyond the schema: the URL must be a direct-download public link with no login, and a 10MB size cap, neither of which appears in the parameter descriptions.

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?

Opens with a specific verb+resource ('Extract structured data from a purchase order') and enumerates the extracted fields (PO number, dates, buyer/vendor, currency, payment terms, totals, line items with SKU/qty/price). An agent can immediately distinguish this from the sibling parse_invoice based on the resource alone.

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?

States clear preconditions: public https URL, up to 10MB, PDF or image, must download directly without a login. It does not explicitly name parse_invoice or say when a purchase order should be parsed versus an invoice, so it stops short of full routing guidance.

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