reply

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

No annotations are provided, so the description bears the full burden of disclosing behavioral traits. It effectively reveals key behaviors: it looks up the original sender by message ID, delivers the reply to their inbox, and optionally pushes it live. This goes beyond the input schema by explaining the internal process. However, it does not mention potential side effects (e.g., what happens if message ID is invalid) or permissions needed.

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?

The description is concise, consisting of two straightforward sentences. It front-loads the core purpose ('Reply to a message in your inbox') and then provides the key mechanic. Every word earns its place; there is no fluff or redundancy.

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?

Given the tool has 3 parameters, no output schema, and no annotations, the description is somewhat complete but lacks details. It explains the main action and one optional behavior (live delivery), but does not describe the response format, error cases, or prerequisites (e.g., must have read messages to get a message ID). For a mutation tool, knowing the return value or acknowledgment would be useful.

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?

All three parameters have schema descriptions with 100% coverage, so the baseline is 3. The description adds some context—explaining that the reply is delivered to the original sender's inbox and can be live—but does not substantially enrich the parameter meanings beyond what the schema already provides. For example, the schema already describes 'deliver_live' as pushing to terminal if live.

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 clearly states the tool's purpose: 'Reply to a message in your inbox.' It specifies the action (reply), the resource (message in inbox), and how it works (looks up original sender, delivers reply to their inbox and optionally live). This distinguishes it from siblings like 'send_message' (which sends a new message) and 'ask' (which might ask a question).

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?

The description implies when to use this tool—when you need to reply to an existing message in your inbox. However, it does not explicitly tell when not to use it or provide alternatives. For example, it doesn't compare with 'send_message' or 'ask'. The guidance is adequate but not explicit.

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