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

Annotations declare this is a non-read-only, non-destructive, non-idempotent write. The description adds behavior annotations cannot convey: the operation is asynchronous and takes minutes, it returns an id immediately rather than the finished app, progress is checked via app_status, and the user can watch the build via a link. That is exactly the async/lifecycle 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?

Four sentences, each carrying distinct load: trigger, scope of generation, async lifecycle, and the sibling routing rule. Front-loaded with the use case before the mechanics.

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 an output schema present, the return-value shape need not be described, and the description instead supplies the workflow the agent must orchestrate (id now, poll via app_status, then deploy_app). For a multi-step async build tool this is complete.

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 idea, name, and mobile fully. The description mentions mobile implicitly ('web (or mobile) app') but adds no format, constraint, or interaction detail beyond the schema. 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 concrete verb and resource ('Generates the full app (screens, API and database)') and gives examples of what counts (booking site, CRM, internal tool). It also distinguishes itself from the similarly named create_app and build_app_from_template siblings by naming the alternative explicitly.

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?

Explicitly names the trigger ('when the user wants a working web (or mobile) app built for them'), the exclusion ('To only open the builder with an idea, use create_app'), and the follow-up path (app_status then deploy_app). Nothing is left to inference.

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