gmail

draft_reply

Create a reply draft to an existing email, maintaining the conversation thread. Use this to compose a response that can be reviewed before sending. Automatically adds 'Re: ' prefix to subject and preserves email threading. The reply_all parameter determines whether to reply to all original recipients or just the sender. Plain text supports markdown formatting.

Input Schema

TableJSON Schema

Name	Required	Description
`email_id`	Yes	ID of the email to reply to (from search_email or get_email)
`body_html`	No	Optional HTML version for rich formatting
`body_text`	Yes	Reply message text. Supports markdown formatting
`reply_all`	No	true: reply to sender and all recipients. false: reply only to sender. Default: true

Output Schema

TableJSON Schema

Name	Required	Description	Default
`id`	Yes
`message`	Yes
`createdMessage`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedApr 7, 2026
- removedInput schema / additionalProperties
```
Removed value: -false
```

Changed1 schema field changedFeb 9, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "createdMessage": {
+      "type": "string"
+    },
+    "id": {
+      "type": "string"
+    },
+    "message": {
+      "additionalProperties": false,
+      "properties": {
+        "id": {
+          "type": "string"
+        },
+        "labelIds": {
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        },
+        "threadId": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "id",
+        "threadId"
+      ],
+      "type": "object"
+    }
+  },
+  "required": [
+    "id",
+    "message",
+    "createdMessage"
+  ],
+  "type": "object"
+}

First observedJan 31, 2026

TDQS

A4.3/5.0

Behavior4/5

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

The description adds valuable behavioral context beyond annotations: it explains the automatic 'Re:' prefix addition, email threading preservation, and markdown support. Annotations already indicate this is a non-destructive write operation (readOnlyHint=false, destructiveHint=false), but the description provides useful implementation details without contradicting them.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is efficiently structured with four sentences that each serve a distinct purpose: stating the core function, explaining the use case, describing automatic behaviors, and clarifying parameter semantics. No wasted words, and key information is front-loaded.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity, comprehensive schema coverage (100%), clear annotations, and the presence of an output schema, the description provides complete contextual understanding. It covers purpose, usage context, key behaviors, and parameter implications without needing to explain return values (handled by output schema).

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 100% schema description coverage, the input schema already documents all parameters thoroughly. The description mentions 'reply_all parameter determines whether to reply to all original recipients or just the sender' and 'Plain text supports markdown formatting' for body_text, adding minor context but not significant value beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('Create a reply draft'), target resource ('to an existing email'), and key behavior ('maintaining the conversation thread'). It distinguishes from sibling tools like 'draft_email' (new email) and 'send_draft' (sending rather than drafting).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear context for when to use this tool ('to compose a response that can be reviewed before sending'), but doesn't explicitly state when NOT to use it or compare it to alternatives like 'send_draft' for immediate sending. The guidance is helpful but lacks explicit exclusions.

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

All gmail tools Inspect

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