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

Annotations cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description goes well beyond them: error semantics (422 for no text/unsupported language, 503 for a missing model, not charged), latency 3-30 s, price USD 0.02 with no free tier, no logging/storage of submitted text, and an explicit prompt-injection caution on returned text.

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?

Purpose and sibling routing are front-loaded, and the semicolon-chained detail is dense but ordered. It loses a point for a stray, irrelevant 'on-chain strings' reference and for retreading 'digital or scanned' already present in the title.

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?

For an 8-parameter, paid, network-dependent tool with an output schema, the description covers everything an agent needs: limits, error codes, cost, latency, privacy, untrusted-data handling, and a docs link. Return-value structure is even explained despite the output schema shouldering that burden.

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 already 100%, so the baseline is 3; the description adds genuinely new constraints not in the schema, notably the 30,000-character per-call limit and the aggregated language code list, and reiterates that `source` should be supplied for scans. Some of this duplicates existing param descriptions, keeping it below 5.

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 precise verb+resource ('translate a PDF document, digital or scanned') plus the output format (Markdown) and language set, which no sibling offers. It also explicitly distinguishes itself from translate_text for plain-text input, so an agent can route without opening a schema.

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?

Names the alternative explicitly ('For plain text use translate_text') and gives the condition for supplying `source` on a scan, plus input limits and OCR guidance. It stops short of a full when/when-not decision matrix, but the routing context is clear.

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