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

Annotations only cover the generic profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false, openWorldHint=true); the description adds real behavior beyond them: login required, synchronous content-safety moderation with violation rejection, SSRF/size/type validation, an avatar-specific review standard that also blocks QR codes and contact-info solicitation, and the concrete failure signal image_content_rejected.

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?

Bracketed 【需要登录】/【何时用】/【限制】 headers front-load the login requirement, the purpose, and the constraints, and every sentence maps to a downstream tool or a rejection condition. It is on the long side, but the density of routing information means little of it is padding.

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 2-parameter tool with no output schema, the description still covers auth, accepted inputs, validation behavior, the rejection path and its error code, and the full downstream wiring of the returned URL. An agent has everything needed to call it correctly and handle failure.

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 baseline is 3. The description goes further by explaining that kind governs storage classification and the moderation口径, and adds the jpg/png/webp-only constraint for moment-image that the schema does not state, giving the agent a reason to pick a value rather than just its allowed set.

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: mirror a public image URL into platform storage and return a stable image address. It also names what it is not (set_organization_logo fetches images itself), so an agent can separate it from the nearest sibling without opening any 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?

The 【何时用】 block gives an explicit two-step workflow (convert URL first, then feed the returned url into update_my_profile / update_my_product / create_product / create_organizer_activity / publish_moment) and an explicit alternative (set_organization_logo for org logos). Conditions selecting this tool versus the alternative are spelled out, not implied.

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