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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), so the description's real contribution is the domain rule that friendships are derived from mutual follows rather than an application/approval state. That is meaningful context an agent could not infer from structured fields, though return shape and pagination limits are left implicit.

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?

Three short sentences, front-loaded with the action and scope, then the definitional rule, then the use cases. Nothing is redundant or padded.

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 simple paginated read with full annotation coverage and no output schema, the description supplies what an agent actually needs: what a friend means here and when to ask for the list. Only the returned record shape is unspecified, which is a minor gap for this complexity level.

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% — both limit (default 20, max 50) and offset are documented in the schema itself. The description adds nothing about paging semantics, so the schema does all the work and 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?

States a specific verb and resource ('列出当前账号在 PowPow 的好友') and then defines the resource precisely: a friend is a mutual follow, with no friend-request flow. That definition alone separates it from siblings like my_followers and my_following without needing to name them.

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?

Gives concrete use cases ('我有哪些好友', '我和谁是互关'), which tells the agent the right situations to call it. It stops short of explicit exclusions or naming the alternative tool for one-directional follow lists, so it is clear context rather than a full routing rule.

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