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

Annotations declare readOnlyHint=false, idempotentHint=true and destructiveHint=false, and the description explains exactly why a 'read' tool mutates: 'A returned reply is marked read by this client.' It further discloses cursor replay behavior and clarifies that reads 'never mean acceptance or change the next actor', which is meaningful semantic context not encoded in any annotation.

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?

Dense and front-loaded: the resource and its limits come first, followed by paging mechanics and then return semantics. Nearly every clause carries operational information, though the sequence of cursor rules is slightly scattered across the middle sentences.

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 covers return shape reasonably (one reply plus sent_message read status, and message=null still returning the status), plus cursor handling. It could say more about what the returned cursor looks like or how end-of-dialogue is signaled, which matters for a paging 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 coverage is 33% (only dialogue_token is documented), so the description must compensate and it partly does: it gives sent_message_id a default ('latest') and explains cursor provenance. However, it refers to the cursor as 'next_cursor' while the schema names the property 'cursor', a naming mismatch that could cause an incorrectly named argument. The motivation for the cursor is conveyed but the parameter names are not consistently anchored to the schema.

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 with explicit scope: 'Fetch at most one next published reply and the read status of one visitor message', then bounds it negatively with 'Never returns full history or visitor text.' An agent can immediately distinguish this from the sibling send_dialogue_message.

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 clear operating context: use the dialogue_token and the optional cursor from the preceding successful result, and save the new cursor only after receiving it. The re-read caveat ('Reusing an old cursor repeats the same reply, even if already marked read') tells the agent when a call will not advance. It stops short of naming an alternative sibling for sending or looking up history.

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