mail-mcp

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draft_update

Replace a draft's recipients, subject, body and attachments (full replacement). Returns a new draft_id; the old one stops working. Requires MAIL_DRAFTS_ENABLED=true.

Instructions

Replace a draft's recipients, subject, body and attachments (full replacement). Returns a new draft_id; the old one stops working. Requires MAIL_DRAFTS_ENABLED=true.

Input Schema

Name	Required	Description	Default
`cc`	No	CC recipients (optional, max 50)
`to`	Yes	Recipient email addresses (1..50)
`bcc`	No	BCC recipients (optional, max 50)
`subject`	Yes	Email subject (1..998 characters)
`draft_id`	Yes	`draft_id` returned by `draft_create`, `draft_update` or `draft_list`
`reply_to`	No	Reply-To address (optional)
`body_html`	No	HTML body (at least one of body_text or body_html required). Separate field from `body_text`: pass the HTML itself, never wrapped in pseudo-tags like `<body_html>`; the server rejects them.
`body_text`	No	Plain text body (at least one of body_text or body_html required). Separate field from `body_html`: never concatenate the two or wrap content in pseudo-tags like `<body_text>`; the server rejects them.
`account_id`	No	Account identifier (defaults to `"default"`)	default
`references`	No	References header for threading (optional)
`attachments`	No	File attachments (optional)
`in_reply_to`	No	In-Reply-To message ID for threading (optional)

Output Schema

Name	Required	Description
`data`	Yes	Tool-specific data payload
`meta`	Yes	Execution metadata (timestamp, duration)
`summary`	Yes	Human-readable summary of the operation outcome

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv0.6.0Oct 22, 2026

changedInput schema / properties / body_html / description

Previous value: -"HTML body (at least one of body_text or body_html required)"New value: +"HTML body (at least one of body_text or body_html required).\nSeparate field from `body_text`: pass the HTML itself, never wrapped\nin pseudo-tags like `<body_html>`; the server rejects them."

changedInput schema / properties / body_text / description

Previous value: -"Plain text body (at least one of body_text or body_html required)"New value: +"Plain text body (at least one of body_text or body_html required).\nSeparate field from `body_html`: never concatenate the two or wrap\ncontent in pseudo-tags like `<body_text>`; the server rejects them."

Addedv0.5.0Oct 15, 2026

TDQS

A4.5/5.0

Behavior5/5

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

With no annotations, the description carries the full disclosure burden and does so well: it states this is a full replacement, that a new draft_id is returned, that the old id stops working, and that the environment flag is required. These are the key behavioral surprises an agent needs to know.

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?

Three short sentences, front-loaded with the core operation and immediately followed by the main side effect and prerequisite. There is no wasted text.

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 rich schema, output schema, and 100% parameter description coverage, the description supplies what it must: replacement semantics, ID invalidation, and the required feature flag. An agent has enough to call it correctly without further description-level explanation.

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?

Schema description coverage is 100%, so the schema already documents all 12 parameters, including attachment handling and body fields. The description adds the important full-replacement framing and ID invalidation, but does not add syntax or per-parameter detail 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 uses a specific verb and resource: it replaces a draft and explicitly states that the operation is a full replacement. That distinguishes it from draft_create, draft_delete, and draft_send without requiring the schema.

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?

It gives clear context for use: replacing an existing draft and requiring MAIL_DRAFTS_ENABLED=true. It does not explicitly name when to use draft_create instead, but the full-replacement framing makes the intended use clear.

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