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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds a genuine trait beyond them: it reads from cached metadata with no network call, which tells the agent results may be stale or empty if the cache is cold.

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?

Front-loaded single sentence stating purpose, followed by a one-line behavioral note and a compact example. No filler, though the example largely restates the schema's format constraint.

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?

An output schema exists, so return values need no explanation, and annotations cover the safety profile. Cache-backed sourcing and the JID format are both addressed, leaving only the sibling boundary (list_groups) unaddressed.

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 coverage is 100%; the schema already specifies the required `jid` and its @c.us format. The description's example ({ jid: "5491155550001@c.us" }) illustrates the format but adds no semantics beyond what the schema states, so the baseline 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 with scope: listing WhatsApp groups a given contact belongs to. This is clearly separable from siblings like list_groups (all groups) and get_contact (contact details), though it never names those siblings to make the boundary explicit.

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 useful context ('reads from cached chat metadata — no network') that implies when this is cheap/safe to call, but offers no explicit when-to-use, when-not-to-use, or named alternative (e.g. list_groups vs this tool). Usage is implied rather than stated.

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