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

Annotations already signal mutation (`readOnlyHint=false`, `destructiveHint=true`), and the description adds meaningful behavioral context on top: it stores the file for fax delivery, requires automation-only invocation, and forbids passing file bytes through the model in chat flows. This goes well beyond what the annotations alone provide.

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 short sentences, front-loaded with the core use case and followed by a hard exclusion. Every sentence earns its place: usage, when-not, the model-bypass constraint, and the side effect. No filler or repetition of schema content.

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?

The description is complete for the tool's complexity: it explains the required follow-up call (`send-fax-uploaded`), the chat-flow alternative, the side-effect behavior, and the operational constraint about model exposure. An output schema exists, so the absence of return-format detail is acceptable.

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 explains all six parameters. The description reinforces that `file_content` is base64 and that the flow returns a path, but it does not add substantial per-parameter meaning beyond schema. Baseline 3 is appropriate.

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 names a concrete action—uploading document bytes as base64 for non-chat integrations—and immediately ties it to the sibling `send-fax-uploaded` via the returned path. It clearly separates this tool from the chat-oriented flow by naming `pipeline_start`, `list-numbers`, `list-contacts`, and `request-file-from-user`, so an agent can distinguish it from siblings without opening schemas.

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?

Usage guidance is explicit and forceful: use this only for automation/non-chat integrations, and never in chat. The description names the exact alternative sequence for chat and even states the reason—file bytes must not pass through the model—so the agent knows both when to use it and when to avoid it.

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