MCP Emails

Set Signature

signature_set

Idempotent

Set or update the email signature for an inbox. Provide the signature as signature_text (plain text) and/or signature_html (rich HTML) — pass either or both; the missing half is derived automatically on send. Pass an empty string for both to clear the signature. Optionally set signature_enabled (default true; set false to stop appending without deleting the text) and signature_reply_mode ('always' = sign every reply/forward, 'first_only' = only the first message in a thread, 'never' = never sign replies/forwards). Setting a signature marks its source as 'manual', which permanently overrides Gmail auto-import for that inbox. sender_name sets the display name recipients see in the From header, e.g. "Evancoe Bot bot@evancoe.com"; it can be set on its own without touching the signature.

Input Schema

TableJSON Schema

Name	Required	Description
`inbox`	No	Inbox email address, an alternative to inbox_id.
`inbox_id`	No	Inbox UUID from inbox_list. Optional when the key has one inbox; pass this or `inbox`, not both — a pair naming different mailboxes is refused.
`sender_name`	No	Display name recipients see in the From header, e.g. 'Evancoe Bot' gives "Evancoe Bot <bot@evancoe.com>". Omit to keep, empty string to clear. Whitespace is collapsed: a tab or newline becomes a single space, as does any run of spaces. Angle brackets and non-printable control characters are removed outright.
`signature_html`	No	HTML signature. Omit to keep, empty string to clear. Derived from the text version when only that is given.
`signature_text`	No	Plain-text signature. Omit to keep, empty string to clear.
`signature_enabled`	No	Whether the signature is appended at all. Defaults to true.
`signature_reply_mode`	No	Signature on replies and forwards; 'first_only' is the default.

Output Schema

TableJSON Schema

Name	Required	Description
`notes`	No	Server notes about how this call was handled — for example an argument that was not applied because the selected action does not accept it. Written by MCP Emails, not taken from any message, and absent when there is nothing to report.
`saved`	No
`inbox_id`	No
`sender_name`	No
`email_address`	No
`signature_enabled`	No
`signature_reply_mode`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 23, 2026

changedInput schema / properties / sender_name / description

Previous value: -"Display name recipients see in the From header, e.g. 'Evancoe Bot' gives \"Evancoe Bot <bot@evancoe.com>\". Omit to keep, empty string to clear. Control characters and angle brackets are DELETED, not replaced, so a tab or newline joins the words around it; runs of spaces then collapse to one. Separate words with spaces."New value: +"Display name recipients see in the From header, e.g. 'Evancoe Bot' gives \"Evancoe Bot <bot@evancoe.com>\". Omit to keep, empty string to clear. Whitespace is collapsed: a tab or newline becomes a single space, as does any run of spaces. Angle brackets and non-printable control characters are removed outright."

Changed2 schema fields changedSep 21, 2026

changedInput schema / properties / inbox_id / description

Previous value: -"Inbox UUID from inbox_list. Optional when the key has one inbox; pass this or `inbox`, not both."New value: +"Inbox UUID from inbox_list. Optional when the key has one inbox; pass this or `inbox`, not both — a pair naming different mailboxes is refused."

changedInput schema / properties / sender_name / description

Previous value: -"Display name recipients see in the From header, e.g. 'Evancoe Bot' gives \"Evancoe Bot <bot@evancoe.com>\". Omit to keep, empty string to clear. Whitespace is collapsed; control characters and angle brackets are removed."New value: +"Display name recipients see in the From header, e.g. 'Evancoe Bot' gives \"Evancoe Bot <bot@evancoe.com>\". Omit to keep, empty string to clear. Control characters and angle brackets are DELETED, not replaced, so a tab or newline joins the words around it; runs of spaces then collapse to one. Separate words with spaces."

AddedSep 10, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Annotations only indicate idempotent and non-destructive write behavior. The description adds substantial behavioral detail: the interaction between text and HTML (missing half derived), empty strings clearing values, signature_enabled toggling append without deletion, reply mode semantics, and the permanent override of Gmail auto-import when marking as manual. It also discloses sender_name whitespace collapsing and character removal. These go far beyond annotation-provided info.

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 comprehensive yet well-organized, front-loading the core purpose and then detailing parameter interactions. Every sentence adds value; there is no fluff or repetition. It balances length with necessity, making it easy for an agent to parse and apply.

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 complexity (7 parameters, several interrelated behaviors, and an output schema), the description covers all necessary aspects: how to set, update, clear, disable, configure reply modes, and set sender name. It also warns about the permanent override. Nothing an agent needs to correctly invoke the tool is missing.

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

Parameters5/5

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

Schema coverage is 100%, so baseline is 3, but the description adds significant meaning beyond the schema. It explains the relationship between signature_text and signature_html (derivation when one is given), the behavior of empty strings (clear vs omit to keep), the interplay of signature_enabled and signature_reply_mode, and the source-marking consequence. It also clarifies sender_name usage and formatting rules. This elevates the semantics well above the schema alone.

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 states a specific verb (set/update), a precise resource (email signature for an inbox), and the scope (including sender_name and reply mode). It clearly distinguishes from the sibling signature_get by implying read vs write. The purpose is unambiguous and immediately actionable.

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 makes the tool's role obvious and provides enough context for an agent to know when to use it (when changing a signature), but it does not explicitly reference alternatives like signature_get or list conditions for exclusion. The lack of explicit alternatives keeps it from a 5, but the purpose is clear enough that usage is well implied.

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

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