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

Annotations already declare readOnly/openWorld/non-destructive, but the description adds substantial context beyond them: the pricing model ($0.01/call via x402 USDC or card key, first 25 free, failed calls free) and the fact that each call is charged so repeats are not free. The 'reads or computes only and changes nothing' line also reconciles with the counterintuitive idempotentHint=false by explaining the cost basis.

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?

Dense and front-loaded — the encoding options, output format, usage, and pricing all appear in a logical order with no filler. It is on the longer side, but nearly every clause carries actionable information for the agent.

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?

Though there is no output schema, the description explicitly states the return value (SVG plus a data URL ready for an <img> tag), covers encoding defaults, and discloses the cost model. Nothing an agent needs to call it correctly is missing.

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% so the schema already documents all five parameters, but the description adds genuine encoding semantics: the mod-103 check symbol for Code 128's numeric subset, and that EAN-13's check digit is computed or verified. These details go beyond the schema's terse field descriptions.

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 (generate) and resource (barcode as SVG), and names both supported symbologies (Code 128, EAN-13) plus their input constraints. Explicitly routes QR users to the sibling qr tool, so the agent can distinguish it without opening either schema.

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?

Gives concrete use cases (shipping labels, product codes, tickets, inventory) and an explicit alternative ('for QR codes use qr'). Provides a worked example (text=AGENT-12345) and notes EAN-13's 12-or-13-digit requirement, so the agent knows exactly when and how to select it.

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