fap_build

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

With no annotations provided, the description must disclose behavioral traits. It mentions the return values (build success, log tail, path) and the use of ufbt, but it does not disclose side effects such as file creation/overwriting, required permissions, or failure behavior. This is a significant gap for a mutation-like build tool.

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 a single, concise sentence that front-loads the core action ('Build a FAP in apps/<appid> with ufbt') and includes the expected return values. Every word earns its place; there is no redundant or vague phrasing.

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 single-parameter tool with no annotations or output schema, the description covers the primary purpose and return values, making it reasonably complete. However, it omits important operational details such as prerequisite conditions (e.g., ufbt installed, app existing) and error scenarios, which would be valuable for an agent.

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?

The schema provides only the parameter name 'appid' with no description. The description adds meaning by embedding appid in the path 'apps/<appid>', indicating it is the app identifier or directory name. However, it does not explain constraints, defaults, or whether the app directory must exist, leaving some ambiguity.

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 clearly states the tool's function: building a FAP for a given app ID using ufbt, with a specific path pattern 'apps/<appid>'. It distinguishes itself from sibling tools like fap_scaffold and fap_deploy by focusing on the build step and explicitly mentions the output contents.

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 implies usage for building a FAP, but it does not explicitly state when to choose this tool over alternatives, such as fap_scaffold or fap_deploy, or provide exclusion criteria. The context signals and sibling names suggest a build step, but explicit guidance is missing.

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