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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and non-destructive behavior. The description adds substantial context: login is required, pagination ends at nextCursor=null, cursor encodes the viewed user, the first page returns total and muted, cards are truncated to 2 comments, truncated results can be retried with a smaller limit, and visibility/blocking rules affect results. This is rich behavioral disclosure beyond the annotations.

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 front-loaded with the login requirement and core behavior, then organized into labeled sections for tool chaining and edge cases. Every sentence contributes useful information without redundancy.

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 3-parameter read tool with no output schema, the description covers what is needed: auth requirement, default parameter behavior, pagination, response fields, truncation handling, and permission-related edge cases. Nothing critical for correct invocation appears 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%, so the baseline is 3. The description adds meaning beyond the schema: userId omission defaults to the caller, the cursor must be passed back verbatim because the target user is encoded in it, and limit can be reduced to recover from truncated responses. These extras raise it above baseline.

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: '某人发过的全部消息圈' and defines scope ('userId 不传 = 我自己'). It distinguishes from get_moment by noting that cards only carry the latest 2 comments and full comments require get_moment. However, it does not explicitly differentiate from other moment-listing siblings like list_moments_feed or search_moments.

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?

Provides a clear usage chain: use get_creator or search_people to get userId, then this tool to see the person's recent activity, then start_conversation to chat. It also points to get_moment for full comment threads. It lacks explicit when-not-to-use guidance against other moment-feed or search tools, but the context is clear.

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