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

Beyond readOnlyHint=true, the description discloses real behavioral traits: muted and archived chats are excluded, total message text is capped at 24,000 characters, and a `truncated` indicator signals omission. It doesn't cover ordering guarantees across chats or how truncation distributes across the per-chat cap, but the annotation bar is met with useful added context.

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 short sentences, front-loaded with scope and filtering rules, then the truncation caveat. No filler or redundant restatement of 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?

With no output schema, the description carries the burden of describing returns and does so adequately: chats newest-first, each with newest messages, plus a `truncated` flag. The exact response structure (chat identity fields, message metadata) is left unstated, but enough is given to call and interpret the result correctly.

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 all three parameters are already documented (including the default of 20 chats and 5 per chat). The description reinforces newest-first ordering and the global character budget that can cause per_chat results to be trimmed, but adds little semantic detail the schema lacks.

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 a specific resource and scope: the user's unread chats, newest first, each bundled with its newest messages. That aggregated unread-digest behavior is clearly distinct from list_chats or read_chat, though it never names a sibling to make the contrast explicit.

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 implied rather than stated — the agent can infer this is the 'catch up on unread' call — but there is no explicit when-to-use versus read_chat/list_chats guidance, and no mention of prerequisites or exclusions beyond muted/archived filtering.

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