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

Annotations already declare the mutation profile (readOnly=false, destructive=false, idempotent=false), so the description's value is in the constraints it adds: Pro+ plan gating, an extra Agency requirement for .exe/.dmg, and the key behavioral fact that a new version reuses the same stable link rather than breaking it. It does not cover failure behavior on invalid parameter combinations, which keeps it short of a 5.

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 most important fact (a stable hosted link) is front-loaded, and almost every clause carries distinct information with no filler. It is dense to the point of being telegraphic ('Pro+; .exe/.dmg etc need Agency'), which slightly hurts first-pass readability but not efficiency.

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 an 8-parameter, all-optional mutation tool with no output schema, the description supplies the mode logic, plan constraints, and the link shape an agent needs to act correctly. The remaining gap is error/edge-case behavior and any note on what the call returns on success.

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 coverage is 100%, so the baseline is 3, but the description goes beyond the schema by encoding the conditional requiredness of parameters (name required only when creating, filename tied to mediaId, downloadId omitted to create). Since the schema marks zero required parameters, this mode-based mapping is genuinely additive information.

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 first clause gives a concrete verb and outcome — hosting a file behind a stable link at <site>/api/downloads/<id> — plus the intended consumer (a Button). It also enumerates the three operating modes (create, new version, roll back), which separates it from siblings like upload_file, list_downloads, and remove_download.

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?

It gives explicit parameter combinations per mode: name+file for new, downloadId+file for a new version, downloadId+currentVersionId for rollback. That is strong when-to-use guidance, but it never states when NOT to use it or names an alternative tool (e.g., use upload_file first to obtain mediaId) — that link is only implied.

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