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

With no annotations provided, the description carries the full disclosure burden. It usefully reveals the exact return value, the precondition that the link must be existing and active, and the current limitation that the PNG image endpoint is unavailable. It does not explicitly state whether using this tool mutates or 'tags' the link, but the 'Returns' phrasing and the image_available=false flag cover the most operationally important behavior.

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?

The description is two short sentences, front-loading the core purpose and then adding the key caveat about the unavailable PNG endpoint. Every clause earns its place and there is no wasted wording.

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 tool with full parameter documentation and an output schema, the description covers the main use case, the precondition, and the current limitation. The main gap is that the schema marks zero parameters as required, and the description does not explicitly state that at least one of id or short_url must be provided, though 'for an existing active link' strongly implies it.

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 schema already documents both id and short_url as existing identifiers. The description adds the 'existing active link' precondition, but it does not clarify whether either parameter is sufficient, which one should be preferred, or what happens if both are supplied. This is adequate but not a strong value-add over the schema.

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?

The description states a specific action and resource: 'Returns qr_tracking_url (?s=qr) for an existing active link.' This clearly distinguishes it from sibling tools like shorten_url or get_link_analytics, since it is specifically about generating a QR tracking URL from an already-existing link.

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?

The description makes clear that this tool operates on an existing active link, so an agent can infer it is not for creating new short links. It also warns that the PNG image endpoint is not live, which prevents misuse. It does not explicitly name alternative tools or state when not to use it, but the context is reasonably clear.

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