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

Annotations already cover read-only/idempotent safety, and the description goes well beyond them: the 200000-byte inline content_text threshold, which MIME types fall back to signed download, exclusions (no input files, internal scripts, cross-task files), and the security rule that signed URLs must not be written into HTML, citation libraries, ZIPs or logs. It also flags the semantic caveat that credit-exhausted artifacts are not full research results.

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 with the action and return values, then constraints, then caveats — a logical order with no filler sentences. It is densely packed into few sentences, bordering on run-on, but every clause carries operational information.

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?

Despite no output schema, the description fully specifies the return shape (download_url, expires_at, GET method, optional content_text), the size/format conditions that determine which shape applies, and expiry behavior. An agent could call this correctly and handle the response without further documentation.

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?

With only 50% schema coverage, the description compensates by constraining artifact_id (must have can_download=true and belong to the same task manifest) and implying task_id scopes that manifest. task_id itself is never explicitly explained, which keeps it below a 5.

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 first sentence names a specific verb and resource (读取…可交付产物) and states exactly what is returned: a short-lived download_url, expires_at and GET method. It also distinguishes the two artifact states (completed task vs. credit-exhausted stop), so the agent knows precisely what it is fetching without opening the 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?

It states the qualifying conditions clearly: the artifact must come from a completed or credit-exhausted task, and only artifact_ids with can_download=true in the same task manifest may be used. It even prescribes the recovery path on expiry (re-fetch the same artifact rather than rebuilding the billed task). It stops short of naming sibling tools to use for other situations, so it is not a 5.

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