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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds genuinely non-obvious behavior: results are ordered newest first, and a page may contain fewer than the limit or be empty while next_cursor still points to older messages — a quirk an agent would otherwise misread as end-of-data.

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 short sentences with zero filler. The ordering and paging model are front-loaded, and the second sentence spends its words only on the one behavior that would trip an agent up.

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?

There is no output schema, so the description carries the return-value burden, and it largely does: it discloses ordering, the existence of next_cursor, and partial/empty page semantics. It does not sketch the message object's shape, which keeps it out of the top band for a tool with no output schema.

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%, so chat_id, limit, and cursor are already documented in the schema itself. The description reinforces the cursor's role as pointing to older pages but adds no format, bounds, or edge-case detail beyond what the schema provides.

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 states the resource and scope precisely — a chat's messages, ordered newest first, returned one page at a time — which is enough for an agent to know this is a chronological history read. It does not name an explicit verb or differentiate itself from siblings like search_messages or get_message, so it falls short of the top band.

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 agent can infer this is the tool for paging through a chat's message history. There is no explicit statement about when to prefer this over search_messages or catch_up, nor any exclusion or prerequisite guidance.

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