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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the agent knows this is a safe read. The description adds genuine behavioral value beyond that: newest-first ordering, V2 pagination scoped to message timestamps, and the chat-scoped ID caveat. No contradiction with annotations.

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?

Two front-loaded sentences with zero filler: purpose, ordering, and pagination model first, then the critical ID-scoping caveat. Every clause earns its place.

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?

Covers the core contract: what is listed, ordering, pagination model, and the chat-scoped ID warning. But there is no output schema to compensate, and the description never addresses return shape or the cursor/offset distinction, which an agent would need to paginate correctly. Adequate but with clear gaps.

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 only 38%, so the description carries extra burden. It does add meaning by explaining that before/after are V2 filters on the message timestamp, which helps for otherwise undocumented string params. But cursor, offset, and limit semantics are left unexplained, and the schema has no descriptions for them either.

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 (List), resource (messages), and scope (a known chat), plus distinguishing behaviors: newest-first ordering and V2 timestamp-based pagination. An agent can readily tell it apart from siblings like messaging_list_chats, messaging_list_recent_messages, and message_get.

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 'in a known chat' precondition implies the agent must first obtain a chat_id from a chat-listing or resolver tool, and the closing note instructs it to keep chat_id for later get/edit/delete/forward/reaction actions. However, no alternative sibling is named and there is no explicit when-to-use vs when-not-to-use guidance.

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