Meridian

Update Email

email_update

Updates an email template's name, subject, and/or preview_text. At least one of those fields is required. Status and design/HTML cannot be changed through MCP. Activate and edit the body in the Meridian dashboard. An active email must keep a subject: clearing it is refused until the email is deactivated in the dashboard. Like a save in the dashboard, it also updates every automation that sends this email, active or not: each Send Email step keeps a copy of the subject, preview text and HTML, and that copy is what sends, so the change applies to the next send. Runs already paused on a Wait keep the version they started with. Takes app_id and email_id from apps_list / emails_list. Returns the same summary shape as email_get.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "app_id": "<app_id>",
      "email_id": "<email_id>"
    },
    "name": "email_update"
  }
}

Input Schema

Name	Required	Description
`name`	No	New display name.
`app_id`	Yes	The app uuid returned by `apps_list`.
`subject`	No	New subject line (may include merge tags). Pass null to clear it, except on an active email, which must keep a subject.
`email_id`	Yes	The email uuid returned by `emails_list` or `email_create`.
`preview_text`	No	New inbox preview text. Pass null to clear.
`organization_id`	No	An organisation uuid or slug. When supplied, `app_id` is resolved within that organisation and may be a slug instead of a uuid, mirroring the Meridian web app.

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 9, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Goes well beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=false) by disclosing the propagation side effect: every automation Send Email step keeps its own copy of subject/preview/HTML, so the edit applies to the next send, while runs paused on a Wait retain their original version. It also documents the refusal condition on active emails, which is exactly the kind of behavioral detail annotations cannot carry.

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

Conciseness4/5

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

Front-loaded with the mutable fields and the minimum-input rule before the longer side-effect explanation, and every sentence carries substantive information. Slight redundancy in restating that app_id/email_id come from apps_list/emails_list, which the schema already documents.

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?

For a mutation tool with no output schema, it closes the important gaps: what cannot be changed, what happens to dependent automations and paused runs, refusal conditions, and that the return value matches email_get's summary shape. An agent has enough to call it correctly and anticipate consequences.

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

Parameters4/5

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

Schema coverage is 100%, so the baseline would be 3, but the description adds a cross-parameter constraint the schema does not encode: at least one of name/subject/preview_text must be supplied. The sourcing hints for app_id/email_id and the null-clearing rules largely duplicate schema text.

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?

States a specific verb and resource ("Updates an email template") and enumerates exactly which fields are mutable (name, subject, preview_text), immediately bounding scope against siblings like email_create and email_get by declaring that status and design/HTML are out of reach.

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?

Gives strong when/when-not guidance: at least one of the three fields is required, status and body edits must go through the Meridian dashboard, and clearing a subject on an active email is refused until deactivation. It stops short of explicitly routing the agent to email_get for reads or naming a dashboard-equivalent alternative, so it is clear context without full alternative mapping.

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

All Meridian tools Inspect

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