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

Annotations already cover safety (readOnlyHint, idempotentHint, destructiveHint=false), so the description appropriately focuses on other behavioral traits: it discloses the $0.005 USDC x402 payment requirement, successful-call pricing, and the base64 + data URI output format. It stops short of explaining x402 payment flow details, but adds significant practical context beyond annotations.

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?

The description is front-loaded with the core purpose and then provides options, pricing, and an HTTPS alternative in compact form. The option list mildly duplicates the schema, but overall the description is efficient and each section contributes useful 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?

For a straightforward generation tool with full schema coverage and annotations covering safety, the description completes the picture by specifying output format (base64 + data URI), byte limits, cost, and an alternate HTTP access path. No output schema exists, but the return format is described adequately.

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%, with all seven parameters, enums, and defaults documented in the input schema. The description lists the option names but adds little semantic detail beyond the schema (e.g., 'size (px/module)' is essentially equivalent to the schema's 'Pixels per module'). Baseline 3 is appropriate when the schema already carries parameter meaning.

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?

The description states a specific verb and resource: 'Generate a QR code' with supported encodings, text limits, and configurable options. No sibling tool performs QR generation, so the purpose is unambiguous without needing explicit sibling 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?

Usage is implied by the clear task ('for any UTF-8 text up to 2953 bytes'), but there is no explicit guidance on when to choose this tool over alternatives or when not to use it. The HTTPS endpoint note adds context but not selection criteria.

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