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

With no annotations, the description carries the full behavioral burden and does well: it discloses the output format (SVG), a hard input limit, capacity variance by error-correction level, and that each call costs $0.003 USDC via x402 (i.e., payment is required). It stops short of describing failure behavior for oversized or non-encodable payloads or the payment flow mechanics.

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 short sentences, front-loaded with the purpose and output format, then constraints, then cost. No filler and nothing buried.

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 simple self-contained generation tool with a fully documented schema and no output schema, the description covers output format, size limits, capacity nuance, and pricing. Only error/failure behavior is left implicit, a minor gap.

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 all three parameters (data, ecl, size) are already documented in the schema; the baseline of 3 applies. The description only echoes the 2,048-byte limit and adds the nuance that capacity shrinks at Q/H levels, which is marginal value beyond what the schema already says.

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 ('QR code generator') and immediately names the return artifact ('a crisp SVG'), so an agent knows both what is produced and in what format. Siblings (dns, lei, vat, etc.) are unrelated utilities, so no differentiation is needed.

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?

The description gives clear selection context: it is for text/URL payloads within a 2,048-byte limit that fit the chosen error-correction level, and it discloses the per-call cost model. It does not state explicit exclusions or when to pick another tool, but no plausible alternative exists among the siblings.

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