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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavior ("Codes are static and never expire"), but says nothing about what is returned — bytes, base64, a URL, or a file reference — which is the key behavioral unknown for a generation tool with no output schema.

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 front-loaded sentences with no filler; the capability list, the usage directive, and the persistence note each carry weight. The middle sentence is slightly verbose but earns its place as an anti-hallucination guard.

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 24-parameter, 9-type generator with no output schema and sparse schema descriptions, the description should map fields to types and indicate the return artifact. It covers the type landscape but leaves both the parameter mapping and the output format entirely unspecified.

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?

With 24 parameters and only 29% schema description coverage, the description is the main place to explain parameter meaning, yet it only names the content categories — which largely restates the existing `type` enum. It never explains which fields belong to which type (e.g. ssid/password/security for wifi, latitude/longitude for geo, first_name/organization/website for vcard) or what body, title, hidden, background, foreground, error_correction and size do.

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 (Create) and resource (a standards-compliant QR code image) and enumerates the payload kinds it supports (url, text, wifi, vcard, email, sms, whatsapp, phone, geo). An agent knows immediately what the tool produces and which payload classes it handles.

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?

"You cannot draw a scannable QR code yourself — always use this tool" is an explicit when-to-use directive that rules out self-generation. It gives no when-not-to-use conditions or alternatives, but the sibling tools (check_json, count_text, diff_text) are unrelated, so there is little to route between.

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