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

Even though annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, the description adds substantial behavioral context beyond those flags: downloadPath is a Bearer-protected API path rather than a public shareable link, visibility rules differ for free vs paid events, and needsReupload means the organizer must re-upload, not that the user lacks permission. This is high-value transparency that the annotations alone cannot convey.

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?

The description is organized into three compact sections — when to use, composition chain, and pitfalls — with no filler. It front-loads the trigger and immediately gives the decision-relevant caveats, so every sentence earns its place.

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 single-parameter read-only tool with no output schema, the description covers what an agent needs to use it correctly: the trigger, the chain, the meaning of lockedCount, the auth requirement on downloadPath, and the paid/free distinction. No critical operational detail appears to be missing.

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 schema already explains activityRef as a slug or id from get_activity/get_signup_activity. The description reinforces per-activity invocation in the chain but does not add any new parameter-level meaning, so a baseline 3 is appropriate.

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 description opens with a precise trigger scenario ('用户问「那场的 PPT/讲义/照片有吗」') and names the exact resource and action: return this activity's materials with visibility tiers and lockedCount. It also situates itself relative to sibling tools (list_my_activity_history, join_activity_online), so an agent can distinguish it from nearby functionality.

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 explicitly says when to use this tool (when the user asks for an event's PPT/handouts/photos) and provides an exact composition chain: call list_my_activity_history, then this tool for every activity with materialsCount>0, and follow with join_activity_online if lockedCount>0 and the user is not registered. This is clear when-to-use guidance with named alternatives.

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