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

Annotations only declare it as a non-readonly, non-destructive, non-idempotent write; the description adds the operational traits that matter: the URL works exactly once, expires in 30 minutes, caps at three open uploads per account, and stays usable after a deploy_project rejected before it starts. Size limits (20 MiB / 50 MiB) and required exclusions (node_modules, .git) are behavioral constraints found nowhere in the structured fields. Consistent with idempotentHint=false.

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?

Front-loaded with purpose and usage, and nearly every clause carries actionable information (expiry, slot limit, size caps, exclusions) with little filler. It is a single very long, heavily nested sentence-paragraph, which costs some scannability for an agent parsing constraints.

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 values need not be described, and the description still covers the full workflow end-to-end: how to execute the upload, what to pass to deploy_project, lifetime and slot constraints, failure recovery, and bundle limits. Nothing an agent needs to call it correctly 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?

The tool takes zero parameters, so there is no per-parameter semantics to explain and the baseline is 4. The description does add value about the data handoff (run the returned command with bash, then pass the returned upload_id into deploy_project), but that concerns the output/next step rather than input parameters.

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 ('Send an app that is on disk to spawnpoint') and immediately frames it as a supporting step for deploy_project, making the boundary between the two tools unambiguous. The agent knows exactly what this produces (an upload URL/upload_id) and why it exists.

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 conditions that select this path over deploy_project's inline files: files exist on disk, more than a few small text files, include images, or exceed the 4 MiB inline cap. It also gives a reuse rule (prefer an existing URL over minting a new one) and the three-slot ceiling, so both when-to-use and when-not-to-use are covered.

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