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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered, and the description adds genuinely useful non-obvious behavior: that some contacts surface as @lid identifiers rather than phone numbers, why that happens, and which field to use for display versus for follow-up calls. It does not mention pagination or whether group chats are included, which keeps it short of a 5.

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 tight sentences: what it returns, then the identifier caveat with the actionable workaround. The non-obvious @lid information is front-loaded rather than buried, and no sentence merely restates the title.

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 needn't be explained, and the description covers the one genuinely confusing aspect (opaque @lid identifiers). The remaining gap is scope: it never says whether group conversations appear here or only in whatsapp_list_groups, which matters for an agent choosing between the two.

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% and both parameters (limit with a stated default of 50, account with a pointer to whatsapp_list_accounts) are already fully documented there. The description adds no parameter-level meaning beyond the schema, 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 ('Lists WhatsApp conversations') plus the payload ('with last message preview'), which an agent can distinguish from reading messages or listing groups. It doesn't explicitly contrast with whatsapp_list_groups or whatsapp_search_messages, but the 'conversations + last message preview' framing is concrete enough to select on.

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?

Usage is only implied: the reader infers this is the entry point before reading messages or searching. The description does give a clear follow-on instruction ('use the JID/chat_id for subsequent calls'), but there is no explicit when-to-use versus whatsapp_search_messages or whatsapp_list_groups, and no stated prerequisites such as having connected an account.

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