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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds traits annotations cannot express: server-side rendering, 'Price: free', and error semantics ('returns isError with a message for invalid input or an upstream failure (not charged)') — the charge-on-failure disclosure is exactly the kind of behavioral context an agent needs.

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?

Single dense paragraph that is front-loaded with what the tool makes and its outputs before moving to mode-specific instructions, cost and errors. Every clause carries information, though the semicolon-chained clauses make it slightly cluttered rather than crisply segmented.

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 9-parameter tool with an output schema, the description covers the gaps that structured data leaves open: which input mode to choose, that rendering happens server-side, that it is free, and how failures surface. Nothing an agent needs in order 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 description coverage is 100%, so the per-parameter meanings (colours, size range, margin, error-correction percentages, enum values) are already documented and baseline is 3. The description goes beyond by explaining the cross-parameter relationship between text, wifi_ssid and the solana: URI form, which the schema only hints at.

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 (make) and resource (QR code) and enumerates the accepted payloads: text, URL, Solana Pay/wallet address, Wi-Fi login. It also names the two output artifacts (PNG base64 data URL or SVG), so an agent knows exactly what this produces. No sibling tool overlaps, so no differentiation burden remains.

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 invocation guidance for the two special modes: 'For Wi-Fi pass wifi_ssid + wifi_password' and 'for Solana Pay pass a solana: URI as text.' This resolves the ambiguity of the multi-mode input, though it offers no explicit when-not-to-use and there are no alternative tools to route against.

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