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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds real value beyond that: it discloses that no build occurs and that the return value is a link, which prevents the agent from assuming this produces an app. It stops short of describing the link's lifetime or any auth/session requirements.

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 short sentences, front-loaded with the usage trigger followed immediately by the negative capability statement and the routing alternative. No 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?

An output schema exists, so return mechanics need not be spelled out, and the description still notes the link return. All parameters are schema-documented and the sibling disambiguation covers the main selection risk for a 60-plus tool workspace.

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% and each of the three parameters is documented in the schema with examples. The description adds nothing parameter-level (e.g. it does not explain how 'idea' should be distilled or when 'mobile' matters), so the baseline 3 applies.

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 (open) and resource (Xenition's no-code app builder) with the qualifier 'pre-filled with their idea, to shape the app by hand.' It also explicitly disclaims what it does not do ('This builds nothing') and names the sibling it differs from (build_app).

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 trigger ('when the user wants to open ... themselves') and an explicit alternative with its own condition ('To have the app built for them from the conversation, use build_app instead'). The when/when-not decision is fully resolved.

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