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

Annotations already mark this as non-readonly, non-destructive, non-idempotent; the description goes further by disclosing that the URL is private, expires in 2 hours, must be consumed via PUT with the returned headers, and enforces per-type size limits. It does not state what happens if you call it twice (idempotency consequence), leaving one behavioral gap.

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?

Front-loaded purpose, then workflow, then expiry, then limits — a natural priority order with no filler. The single paragraph is dense but every sentence carries operational information an agent needs.

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, and the description compensates fully by naming the three returned values (upload_url, the headers, upload_id) and how each is used. Combined with the flow and limits, an agent has everything needed to invoke and consume the result.

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 adds real meaning: the per-type size limits (image 5MB, mp4 75KB–200MB, PDF 100MB) directly constrain size_bytes and explain why content_type defaults from type. The alt_text mention is about a sibling's parameter rather than this tool's.

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 ('Returns a private, short-lived upload URL') plus the concrete input cases it handles (carousel PDF, image, mp4) and explicitly distinguishes itself from save_draft by naming save_draft as the downstream consumer. An agent can tell this is the pre-upload URL-minting step, not the media-attaching step.

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 the exact when ('a file that has no public HTTPS link'), the end-to-end invocation path (HTTP PUT of raw bytes to upload_url with the returned headers), and the alternative routing ('upload_id is then accepted by save_draft as media: [{ upload_id }]'). Nothing about choosing this vs siblings is left to inference.

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