upload_link

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

Goes well beyond the annotations: the link is single-use, for one file, valid 10 minutes, and 'changes nothing else' — confirming the destructiveHint=false / non-persistent nature with concrete lifetime semantics. It also discloses the side-effect boundary (must be sent via the code tool) that no structured field captures.

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?

Three sentences, front-loaded with purpose, then procedure, then constraints and param tips. No sentence is redundant with another, and the operational warning ('works once, for one file, for 10 minutes') is given its own short sentence.

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 mutating, closed-world tool with an output schema and full param coverage, this covers everything an agent needs: what to call, when, the next step, the lifetime constraint, and the pre-upload validation behavior. Return values are already handled by the output schema, so nothing material 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?

Schema coverage is 100%, so both optional params are already documented, but the description adds the rationale for supplying them: they let the server refuse an unsendable file before upload is attempted. That 'why' is genuine added meaning over the schema's terse field text.

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 ('Get a one-time link to upload a file') and pins the scope precisely: a file the user dropped into this chat, destined for an email attachment. An agent can distinguish this from siblings like 'attachment' or 'draft' from the description alone, since it clearly names the upload-link step in the workflow.

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?

Gives clear context for when it applies (the user dropped a file into the chat) and names the follow-up tool explicitly ('then attach it with draft(attach_upload=[its name])'), routing the agent across tools. It stops short of stating exclusions or naming a competing tool to avoid, so it is clear context rather than a full when/when-not rule.

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