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

Annotations already declare readOnlyHint=false and destructiveHint=false, and the description adds substantive behavioral context: the call creates a first-class reply message, implies acknowledgment of the original, and that lease_id fences a stale worker. That is real value beyond the structured fields.

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 dense sentences with the core action front-loaded and the lease-fencing detail following. No wasted words, though the parenthetical note is compact enough that it 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?

With an output schema present, return values need not be explained, and annotations cover the safety profile. The description supplies the mutation intent, acknowledgment implication, and lease fencing, leaving only minor gaps around message/message_id semantics.

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 50%: 'as' and 'lease_id' are documented, but 'message' and 'message_id' carry no schema description. The description compensates for lease_id by explaining where it comes from (messages[0].lease.lease_id in the bus_inbox response) and its fencing role, but says nothing about message/message_id semantics.

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 (reply) and resource (a message received via bus_inbox) and distinguishes the action from a plain send by noting it creates a first-class reply message and implies acknowledgment. It does not name the sibling it is contrasted with (bus_send/bus_ack), so it stops short of 5.

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?

Clearly ties usage to messages obtained via bus_inbox and explains the lease_id fencing purpose (fencing a stale worker), giving concrete context for when to invoke it. No explicit when-not or named alternatives, so not a 5.

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