wechat_known_users

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

With no annotations, the description carries the full burden. It discloses the core behavior (listing users with context tokens) and the dynamic nature ('currently have'). The verb 'List' implies a read-only operation, and the parenthetical exposes the practical significance, which is sufficient for this simple list tool.

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 a single sentence that conveys the action, scope, and purpose without any fluff. The parenthetical adds value in a compact way. It is perfectly sized for the tool's simplicity.

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?

This is a simple no-parameter, no-output-schema tool. The description fully covers what the tool returns and why it matters. No further context (e.g., pagination, permissions) seems necessary given the trivial complexity.

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?

The tool has zero parameters (schema is empty), so the baseline is 4. The description adds no parameter details, but none are needed. The output is implicitly described as user IDs, which aligns with the tool's purpose.

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 uses a specific verb 'List' with a clear resource ('user IDs we currently have a context_token for') and adds a clarifying parenthetical ('i.e., who can be messaged back'). This distinguishes it from sibling tools like wechat_pending_messages and wechat_send_text, making the purpose unmistakable.

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 description provides clear context for when this tool is useful: identifying users who can receive messages. While it does not explicitly name alternatives or exclusions, the 'who can be messaged back' clarification implies its role in messaging workflows, giving the agent enough to infer appropriate usage.

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