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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds real context beyond that: newest-first ordering, the meaning of name_source values, and when phone_jid/lid_jid are null. It stops short of noting any pagination or result-cap behavior, which is the only gap.

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?

Purpose and ordering are front-loaded, then usage, then the alternative — a sensible order. The long parenthetical enumerating contact fields is dense, but it earns its place because there is no output schema.

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?

With no output schema, the description fully documents the returned shape (chat_jid, last-message preview, name, canonical_jid, phone_jid/lid_jid, phone_display) and the ordering, which is everything an agent needs to consume the result correctly for a one-parameter read tool.

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 the schema itself explains limit ('Number of chats to return (e.g. 20). Keep it small to save context'), so the baseline of 3 applies. The description adds nothing about the limit parameter beyond what the schema already says.

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 the user's most recent WhatsApp chats (people and groups)') plus the ordering ('newest first') and the exact return fields. It is clearly separable from read_chat_history and get_unanswered_chats, both of which it names.

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 three concrete use cases ('what's new', finding a chat's JID before read_chat_history, picking up recent conversations) and explicitly routes the unanswered-reply case to get_unanswered_chats instead.

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