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Duplicate post

duplicate_post

Copies any draft or published post into a new unpublished draft, preserving its title, subtitle, body, and settings so you can edit a duplicate without changing the original.

Instructions

Copy any post into a new draft.

Makes a new draft with the title, subtitle, body and settings of a draft or published post, as Duplicate in the post list does. Substack puts [COPY] in front of the title; change it with update_draft. Nothing is published or sent.

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": {
      "post_id": "<post_id>"
    },
    "name": "duplicate_post"
  }
}

Input Schema

Name	Required	Description	Default
`post_id`	Yes	Post ID from list_posts.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 24, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true), and the description adds two pieces of context annotations cannot express: the resulting title gets a '[COPY]' prefix, and 'Nothing is published or sent' scoping the operation to drafts only. It doesn't state that repeated calls create multiple drafts (relevant since idempotentHint=false), which would have completed the picture.

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, each doing distinct work: what it copies, the title side effect, and the reassurance about publishing. The core action is front-loaded with zero filler.

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

Completeness4/5

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

For a one-parameter tool with full schema coverage and existing annotations, the description covers the mutation's behavior, its visible side effect, and the natural next step. The one gap is that with no output schema it never says what comes back (presumably the new draft's ID), which an agent needs to chain into update_draft.

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 coverage is 100% and the single parameter is documented as 'Post ID from list_posts', which already tells the agent where to source it. The description adds no format, constraint, or behavior detail about post_id beyond that, so this sits at the documented baseline.

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 ('Copy any post into a new draft') and immediately enumerates what is carried over: title, subtitle, body and settings. This clearly separates it from create_draft (blank draft) and update_draft (edits an existing draft).

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 a clear usage context ('as Duplicate in the post list does') and points to update_draft for the follow-up rename, which is genuinely actionable routing. It does not explicitly contrast with create_draft when the agent wants a fresh post, so it falls just short of full when/when-not guidance.

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