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

Annotations already declare readOnly/idempotent/non-destructive/non-open-world, so the safety profile is covered. The description adds genuinely new behavioral context: it does not create a short link, and it returns the image plus a permanent embeddable image URL. No rate limits or error behavior, but the key output trait is disclosed.

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 tight sentences: what it makes, what it supports, what it returns, and the routing rule. Front-loaded with the core action and zero 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?

With no output schema, the description carries the return-value burden and does so ('the image plus a permanent image URL that can be embedded with <img src>'), while constraints like char limit and size range live in a fully documented schema. Nothing material for correct invocation 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 baseline is 3, but the description goes beyond the schema by enumerating acceptable payloads for the required 'data' parameter (URL, Wi-Fi string, phone, email, plain text) and confirming the color/size/SVG options. That adds semantic value the schema's terse property descriptions do not.

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 ('Make a QR code image') and immediately scopes it against the sibling: 'without creating a short link' vs. 'Use generate_qr instead when scans should be counted.' An agent can separate this from generate_qr 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 an explicit exclusion rule plus the named alternative: use generate_qr when scans should be counted, use this tool otherwise. That is the exact when/when-not/alternative structure the dimension asks for.

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