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

Goes well past the annotations: failure behavior (file refused, never added, nothing charged, re-encode to MP4/PNG/JPEG), cost ('no tokens'), return payload fields, and a concrete error-diagnosis path (bare '000' means storage host unreachable). The 'safe to call again' note sits alongside idempotentHint=false but is about safety/cost rather than state, so it reads as compatible context rather than a contradiction.

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?

Purpose and WHEN are front-loaded and nearly every sentence carries operational weight (route-specific failure handling, retry rule, cost). It is dense and somewhat long for a one-parameter tool, and the closing 'AFTER THIS the url works as any input of its kind' partly restates the earlier return-value 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?

No output schema exists, and the description fully compensates by enumerating returned fields (url, size, kind, width/height, duration_seconds for video). Combined with failure semantics and retry cadence, an agent has everything needed to call it correctly and interpret 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 description coverage is 100% and the single `id` param is already documented as 'the id upload_media returned'. The description reinforces that provenance but adds no new syntax, format, or edge-case meaning 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?

Opens with a specific verb + resource: 'Checks the file uploaded to an upload_media target and makes it usable.' It explicitly ties itself to the sibling upload_media as the second half of a two-step flow, so an agent can distinguish confirming from uploading without inspecting either schema.

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?

A dedicated WHEN clause states the exact trigger (curl printed 2xx, or user says the browser_upload_url page is done), plus retry timing ('wait a few seconds and call once more') and a negative rule ('DO NOT CALL upload_media AGAIN'). It also branches guidance by upload route (curl vs browser), which is exactly the decision an agent faces.

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