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

Annotations already cover mutation (readOnlyHint=false) and non-idempotency, and the description adds valuable context about the session being one-time and avoiding credential exposure. It goes beyond the structured annotations without contradicting them, though it doesn't detail session lifecycle or auth requirements.

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?

Two sentences with no filler: the first identifies the tool's purpose and constraint, the second gives routing guidance. Information is front-loaded and every clause earns its place.

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 fully documented parameters and an output schema present, the description covers the remaining essential context: what the session is for, that it is one-time, that it hides credentials, and that it is not meant for direct user invocation. Nothing critical is missing for an agent to decide whether to call this tool.

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 fully documents all parameters including filename, size_bytes, typology, and mime_type. The description adds no parameter-specific detail beyond the schema, so the baseline of 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?

The description states a specific action ('mint a one-time upload session') and a clear resource/session type, while explaining its role in enabling the file upload form to send files without exposing credentials. It also distinguishes itself from user-facing tools by being labeled a 'Widget-only helper' and a non-direct-use utility.

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 explicitly says this is 'not intended for direct use' and directs the agent to prefer 'Upload a File → Get a Link & QR' instead. This provides clear when-not-to-use guidance and names the preferred alternative.

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