mcp-whatsapp

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

Annotations already indicate destructiveHint=true (mutation) and idempotentHint=false (non-idempotent), so the agent knows this is a non-idempotent destructive operation. The description adds context by specifying blocking can be done via phone number or JID, which clarifies the target parameter. However, it doesn't disclose additional behavioral traits like rate limits, authentication needs, or what 'blocking' entails (e.g., prevents messages).

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, efficient sentence that directly states the tool's purpose with zero wasted words. It's front-loaded and appropriately sized for a simple action tool, making it easy to parse quickly.

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?

Given the tool has destructive annotations and no output schema, the description is minimally complete but lacks details on outcomes (e.g., what happens after blocking, error conditions). It covers the basic action and parameter scope, but for a destructive operation, more context on effects would be beneficial.

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%, with the 'jid' parameter fully documented in the schema. The description mentions 'phone number or JID', which aligns with but doesn't add meaning beyond the schema's description of JID formats. No additional parameter details are provided, so it meets the baseline for high schema coverage.

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 clearly states the action ('Block') and resource ('a contact'), specifying it can be done 'by phone number or JID'. It distinguishes from sibling 'unblock_contact' by indicating the opposite action. However, it doesn't explicitly differentiate from other blocking-related tools like 'get_blocklist', which might be a minor gap.

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 no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., contact must exist), when not to use it, or compare with related tools like 'get_blocklist' for checking blocked status. Usage is implied but not explicitly stated.

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