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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial context beyond them: error-correction level M, scan-appropriate scaling, the 2 KB input ceiling with a 400 response that is never billed, and per-call pricing in USDC via x402 across named chains. This is exactly the billing and failure-mode detail an agent needs before spending.

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 sentences, front-loaded with the trigger condition, then the return format, then limits and cost. Every sentence carries distinct information with no redundancy.

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?

An output schema exists, yet the description still names the return forms (SVG/PNG, base64 and data URI) and covers limits, error behavior, and pricing. Nothing an agent needs to call this correctly is absent.

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 both 'data' and 'format' are already documented in the schema; the description's '2 KB' and 'SVG or PNG' merely restate them. Per the rubric, 100% coverage sets the baseline at 3 when the description adds no new parameter syntax.

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 ('get a QR code') and narrows the use case to 'a link, address or payment string.' No sibling tool competes for this function, so the purpose is unambiguous without differentiation.

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?

'Use when an agent needs a QR code for a link, address or payment string' gives clear usage context. There are no alternatives to route away from among the siblings, but no explicit when-not or exclusion is offered, so it falls short of a 5.

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