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

Annotations only declare the safety profile (not read-only, not destructive, not idempotent), so the description carries the rest and does so well: cost (1 credit, 5 free calls/month), input limits, the detection heuristic that can cause silent misses, and the return contract (download_url valid 24 hours plus table count). These are exactly the operational facts an agent needs before spending credits.

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?

Three tight sentences organized as action, input/constraints, return/cost. No filler, and the constraints and cost are front-loaded enough to be seen before invocation.

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?

Despite an output schema existing, the description still summarizes the return (download_url with expiry, table count), and it covers input limits, cost, and failure conditions. For a single-parameter tool with sparse annotations, nothing material 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 coverage is 0% and the single parameter has no description in the schema, so the description must compensate entirely. It does: 'the PDF file's contents as a base64-encoded string' defines the encoding, and 'max 25 MB, 500 pages' bounds the value.

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 and resource ('Extract all tables detected in a PDF into an Excel (.xlsx) workbook') and adds the output shape ('one worksheet per table'). This is unmistakably distinct from the sibling tools (images_to_pdf, merge_pdfs, pdf_form_fill), none of which touch table extraction.

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?

It gives concrete preconditions for success — tables must have 'visible ruling lines or clearly aligned columns' — plus size limits (25 MB, 500 pages), which tells the agent when this tool will and won't work. It does not explicitly state when to prefer an alternative, but the sibling set offers no overlapping capability, so the omission is minor.

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