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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds real behavioral context beyond that: results are age-independent ('regardless of age'), and it discloses the returned payload shape (chat/link, why addressed, related item, message with attachments). Pagination continuation via nextCursor/hasMore is also stated.

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?

It is one dense run-on sentence, but it is front-loaded with purpose, then usage intent, then paging behavior. Every clause earns its place, though the parenthetical enumeration makes it heavy.

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, yet the description explicitly describes what a returned item contains (chat and link, why it is addressed, related item, the message with attachments), compensating for the missing schema. Combined with the paging behavior and the read-only annotation, an agent has everything needed to call it 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 coverage is 100%, so limit and cursor are already documented, and the baseline is 3. The description's pagination note refers mostly to the response fields (nextCursor/hasMore) rather than adding syntax or constraints to the parameters themselves, so it does not clearly exceed baseline.

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 (Returns) and resource (messages addressed to the token owner still unanswered), and enumerates the trigger types — direct chat, mention, reply — that qualify. An agent can distinguish this from chat_read and chat_send without opening any schema.

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 a clear triggering condition: 'Useful when the user asks what awaits their reply.' This maps the tool to an intent. However, it names no alternative (e.g., chat_read) and gives no exclusions, so it stops short of full when/when-not guidance.

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