Send a response to the latest inbox email or a given mail_id, delivering your message to the sender's session. Solves the need to answer mail directly within the agent coordination workflow.
Reply to the latest inbox mail (or a mail_id) by sending to its sender session.
| Name | Required | Description | Default |
|---|---|---|---|
| agent | No | ||
| mail_id | No | Inbox mail id to reply to; omit to use the latest | |
| message | Yes | ||
| session_id | No |
Changes observed during successful MCP inspections.
v0.11.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries full burden. It does reveal the core behavior (sending to the sender session) but does not disclose side effects, error modes, or the role of agent/session_id. For a mutating action with no annotations, this is under-specified.
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?
One sentence, efficient, front-loaded with the main behavior. Loses a point because the 'sender session' concept is introduced without explanation.
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 annotations Schema, sibling send_message presumably alternative, and two unexplained parameters (agent, session_id) plus no output schema, the definition is under-specified. It doesn't clarify when to choose reply vs send_message or what session_id refers to.
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 only 25%, so description carries weight. It clarifies mail_id ('Inbox mail id to reply to') is redundant with schema, and adds the sender-session targeting contextsac. But agent and session_id remain unexplained, leaving ambiguity about whether session_id refers to the sender session and how agent fits.
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 names a clear action ('reply') and a target resource (inbox mail, either latest or specified by mail_id), and explains the mechanism (sending to its sender session). It is understandable on its own, but it doesn't explicitly differentiate itself from sibling tools like send_message or await_reply beyond the reply-to-mail concept.
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 states when to use it (to reply to latest mail) but offers no guidance on when not to use it, no alternatives, and no requirements such as needing an existing session or the meaning of session_id. The agent is left to infer conditions like 'session must already exist'.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.