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

Annotations already declare readOnlyHint=true and openWorldHint=false; the description adds genuinely new guarantees that matter here — nothing is stored and nothing is charged. It also names the screening criteria (format, pages, words, scanned pages). It stops short of saying whether repeat calls are rate-limited or whether results are cached.

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 sentences, zero waste, with the most decision-relevant fact (free, no charge) front-loaded. Nothing could be cut without losing information.

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?

With no output schema, the description correctly states what comes back: a price or the reason it can't be processed. That covers the main return contract; the shape of the price response (currency, breakdown) is left implicit but not essential for invocation.

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 100%, including the max-5-images/10 MB constraints and base64 encoding, so the schema does the heavy lifting. The description's mention of formats and pages loosely mirrors the schema but adds no format syntax or size detail beyond it.

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+resource: screens a file and returns a price or a rejection reason. It's clear what the tool does, though it doesn't explicitly contrast itself with create_order, the obvious next step in the sibling set.

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?

"Free price check" implies this is the pre-purchase step before create_order, but the description never says so outright and offers no explicit when-not-to-use guidance. Usage is inferable rather than stated.

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