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

Annotations declare readOnlyHint=false and destructiveHint=false, so safety is partly covered, but the description adds genuinely useful behavior beyond that: the URL/token are short-lived, bytes must be PUT raw with the correct Content-Type and no base64, and crucially nothing is recorded until finalize so an abandoned upload leaves no artifact. It stops short of stating permissions required or the exact expiry window, hence 4.

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?

Dense and front-loaded: the selection condition, return values, invocation steps, and lifecycle guarantee are all present with no filler sentences. The API reference link is the only extra and is proportionate.

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?

No output schema exists, yet the description explains what is returned (signed upload URL plus upload_token) and the exact follow-up call needed. For a two-step upload flow with a mutation side-effect, the description covers everything an agent needs to avoid stranding an upload.

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 documents all four parameters (name, task_id, mime_type, size_bytes). The description echoes task_id, name and upload_token in workflow context but adds no syntax or format detail beyond what the schema provides, so the baseline 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?

States a specific verb and resource ('Get a signed upload URL') and immediately distinguishes itself from the sibling add_artifact by naming the size threshold (~6 MB) that selects it. An agent can tell exactly what this tool does and when it is the right one.

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?

Names the alternative (add_artifact inline base64 path), the condition that selects this tool (files too big for that path, with examples), and the downstream step (call add_artifact with the same task_id, name, upload_token). The full two-step workflow is spelled out, leaving nothing to inference.

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