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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds genuinely useful non-annotation context: the output is a PNG at error correction level H, and it explicitly states no API key/account/signup is required and that it can be called directly, which reduces invocation friction.

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 tight sentences, front-loaded with the core action and output format, followed by the access prerequisite. No filler.

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 one-parameter tool with read-only/idempotent annotations and no output schema, the description covers purpose, output format, and access requirements. It stops short of noting the input length limit, but is otherwise sufficient for correct 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 0%, so the schema documents no parameter semantics. The description says the input is 'a text or URL' but does not mention the 1-2000 character bounds or that 'text' is the sole required field. Baseline consideration of a single-param tool keeps this at 3, but the description does not fully compensate for the coverage gap.

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 ('Make a QR code for a text or URL') and adds the output format (PNG, error correction level H). This clearly distinguishes it from the sibling read_qr_code, which does the inverse.

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?

Implies the use case (encoding text/URL into a QR image) but offers no explicit when-to-use or when-not guidance, nor does it name alternatives. Adequate but leaves routing to inference.

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