Substack MCP vs Posterly
A side-by-side look at the Substack MCP and Posterly MCP servers: transport, auth, tools, quality signals, and the config to install either one in Claude, Cursor, Windsurf or VS Code.
Verdict: choose Substack MCP for social media work as a local process; choose Posterly for social media as a local process. You can also run both side by side in one mcpServers block.
Which MCP server should you choose?
Choose Substack MCP when
- You need dedicated capabilities in the Social Media domain.
- You prefer a local stdio subprocess transport.
- Its auth model fits you: other.
- You have the keys it needs:
SUBSTACK_PUBLICATION_URL, SUBSTACK_SESSION_TOKEN, SUBSTACK_USER_ID, SUBSTACK_MCP_HOME. - You want tools like
get_subscriber_count, list_published_posts, list_drafts.
Choose Posterly when
- You need dedicated capabilities in the Social Media domain.
- You prefer a local stdio subprocess transport.
- You have the keys it needs:
POSTERLY_API_KEY. - You want tools like
get_agent_signup_info, start_signup, get_signup_session.
Feature & specification comparison
Rows where the two servers differ are marked.
| Spec | ||
|---|---|---|
| Category | Social Media | Social Media |
| Quality signal | 68/100 · Great | 63/100 · Good |
| Install command | Confirmed | Confirmed |
| Transport | Local subprocess (stdio) | Local subprocess (stdio) |
| Auth | other | Not declared |
| Pricing | Free | Not declared |
| Required env vars | SUBSTACK_PUBLICATION_URLSUBSTACK_SESSION_TOKENSUBSTACK_USER_IDSUBSTACK_MCP_HOME | POSTERLY_API_KEY |
| Verified owner | Community listing | Community listing |
| GitHub stars | 44 | 0 |
| Directory activity | 6 views 0 installs 0 upvotes | 1 views 0 installs 0 upvotes |
| Tools | 14 | 67 |
| Full listing | View Substack MCP | View Posterly |
Tools & capabilities
Substack MCP tools 14
get_subscriber_countGet the current subscriber count for your Substack publication. Returns `precision`: 'exact' when the API reports a true count, 'approximate' when only Substack's rounded value is available (the real number is that or higher — render it hedged, e.g. '1,000+'), or 'unavailable' with count -1. Never treat an approximate value as exact.list_published_postsList published posts with pagination. Returns title, date, slug, and URL for each post.list_draftsList draft posts. Returns title, creation date, and audience for each draft.get_postGet the full content of a published post by ID. Returns title, body HTML, metadata.get_draftGet the full content of a draft post by ID. Returns title, body, metadata.get_post_commentsGet comments on a published post. Returns commenter name, comment body, date, and reaction counts.get_sectionsList your publication's sections (categories). Returns each section's id and name. Use a section id as `section_id` when creating or updating a draft to file it under that section.get_post_analyticsGet performance stats (views, emails sent/delivered/opened, signups, subscribes, estimated value, comments, reactions) for a published post by ID. Substack has no per-post stats endpoint, so this searches your 500 most recent published posts for the ID; returns a not-found note if it isn't among them.list_scheduled_postsList posts scheduled for future publication, soonest first. Read-only visibility into what's queued — scheduling itself is done in Substack's editor (this server does not schedule, publish, or delete long-form posts). Returns id, title, audience, and scheduled time (`trigger_at`).create_draftCreate a new draft post. Accepts markdown body which is converted to Substack's format. Does NOT publish — creates a draft only.update_draftUpdate an existing draft post. Only works on unpublished drafts. Accepts markdown body.upload_imageUpload an image to Substack's CDN. Provide exactly one of `image_base64` (a base64 data URI) or `image_path` (a local file path). Returns a hosted image URL that is publicly fetchable by anyone with the link (an unlisted asset — not attributed to you or added to your feed).- +2 more on the listing page
Posterly tools 67
get_agent_signup_infoExplain how to use posterly MCP for agent-led signup before an API key exists, including the safe human-in-the-browser boundaries.start_signupStart the public posterly paid signup flow for a user before posterly API access exists. Returns a signup poll URL, a browser Checkout fallback URL, and, when enabled, a prepaid PaymentIntent the agent can pay with a Link Agent Wallet virtual card (credential_type: card). The user still sets a password and approves social OAuth in the browser. Never ask for card numbers, a posterly password, or social passwords in chat.get_signup_sessionPoll a public posterly signup session created by start_signup. Use this to narrate payment (Link virtual card or browser Checkout), password setup, and agent access status before a posterly API key is installed. Keep updates user-facing; do not narrate raw HTTP, curl, or API plumbing.whoamiWho you are and how posterly is connected. view=identity (default): the authenticated user, API key scopes, workspaces, and onboarding next step. ALWAYS call this at the start of a session; if onboarding.completed is false, walk the remaining onboarding steps IN THIS conversation (about you, connect, brand voice, first post) and do not send the user to /onboarding-v2 or the dashboard composer wizard. view=status: MCP server version, latest npm version, endpoint and API key health, and update guidance; works before POSTERLY_API_KEY is configured.list_accountsConnected social accounts and what posterly has learned about them. view=accounts (default): connected accounts, optionally one workspace_id or one account_id; Instagram rows identify direct-login versus Meta-linked connections and whether native media tags/collaborators are available, so check this before Instagram user_tags or collaborators. view=learned_voice (account_id): the voice learned from the account's real published captions (summary, traits, style guidelines, habits); read-only, never overwrites the saved brand profile. view=performance_profile (account_id): 90-day coaching stats, engagement-rate trend, and summary (Pro plan or higher; platforms without per-post analytics never get one). view=connect_session (session_id): poll a session from create_connect_session and keep the user updated in plain language; stop when status is connected, failed, cancelled, or expired.disconnect_accountDisconnect a connected social account from posterly. DESTRUCTIVE and IRREVERSIBLE: removes the account connection, emits account.disconnected webhooks, and may transfer Instagram scheduled posts to a replacement account. REQUIRED BEFORE CALLING: Call `list_accounts` first, show the user the exact platform, username, account ID, and workspace that will be disconnected, then get explicit confirmation. Pass confirm=true only after that confirmation.connect_accountConnect a credential-based social account (telegram, bluesky, discord, wordpress, devto, hashnode, lemmy) directly, without a browser session. Call list_platforms with view=connect_link first to discover the exact credential fields the platform needs. Prefer scoped secrets: app passwords (Bluesky, WordPress), bot tokens (Telegram), webhook URLs (Discord), and API tokens (Dev.to, Hashnode) over primary passwords. Warn the user that any credential they share passes through this conversation. For OAuth platforms (Instagram, X, LinkedIn, ...) use create_connect_session instead.create_connect_sessionCreate a short-lived posterly dashboard handoff session for connecting a social account. Send the secure connection URL to the user, then poll list_accounts with view=connect_session to narrate progress. Do not ask for social media passwords or OAuth codes; posterly handles those browser steps.create_api_keyCreate a new posterly API key for the authenticated user. SECRET-CREATING WRITE: only use after explicit user confirmation. The new key can only request scopes already present on the calling dashboard-created API key; OAuth and managed assistant tokens cannot mint keys. Team management (members:read, members:write) and client portal sign-in link permissions are never copied or granted here: a person turns them on in /dashboard/api.delete_api_keyRevoke a posterly API key owned by the authenticated user. DESTRUCTIVE: call whoami or use a known key ID, show the user the exact key ID/prefix/name if available, and get explicit confirmation before calling. Cannot revoke the key currently authenticating this request, OAuth-issued keys, or managed assistant keys.list_workspace_membersList the people in a workspace: members (with role, status, brand access and API access) and pending invites, plus seats in use. API access says whether a teammate can use this workspace's API plan from their own keys and AI apps; owners and admins also see each member's key count, connected AI apps and last use. Needs an API key with the Manage team permission. Any workspace member can list; brand-limited teammates only see brand ids they can access.manage_workspace_memberInvite, update, or remove a workspace colleague. This SENDS EMAILS and CHANGES WHO CAN ACCESS the workspace. Needs an API key with the Manage team permission, and the caller must be a workspace owner or admin. ALWAYS preview first: call without confirm, show the preview to the user, and only call again with confirm: true plus the returned preview_id after the user explicitly approves. action=invite: email and role required (publisher, editor or viewer), optional brand_ids and resend; always sends a pending invite email, never adds anyone instantly. action=update: member_id or invite_id (from list_workspace_members) plus role and/or brand_ids; or member_id plus api_access (true or false, on its own) to turn API and AI app access on or off for that teammate, which lets them use the workspace API plan from their own keys and AI apps (off by default; you cannot change your own; only the owner can change it for an admin; turning it off stops their keys, AI app connections and webhooks for this workspace). action=remove: member_id (removes the teammate and revokes their API keys for this workspace) or invite_id (cancels a pending invite). Admin seats can only be granted in the posterly dashboard. The workspace owner is emailed about every change.- +55 more on the listing page
Ready-to-paste client configs
Paste either block (or both) into your client config, e.g. claude_desktop_config.json or ~/.cursor/mcp.json. We only show a config when the install command is confirmed.
Substack MCP
{
"mcpServers": {
"conorbronsdon-substack-mcp": {
"command": "npx",
"args": [
"-y",
"@conorbronsdon/substack-mcp"
],
"env": {
"SUBSTACK_PUBLICATION_URL": "YOUR_SUBSTACK_PUBLICATION_URL_HERE",
"SUBSTACK_SESSION_TOKEN": "YOUR_SUBSTACK_SESSION_TOKEN_HERE",
"SUBSTACK_USER_ID": "YOUR_SUBSTACK_USER_ID_HERE",
"SUBSTACK_MCP_HOME": "YOUR_SUBSTACK_MCP_HOME_HERE"
}
}
}
}
Posterly
{
"mcpServers": {
"posterly-2": {
"command": "npx",
"args": [
"-y",
"posterly-mcp-server@latest"
],
"env": {
"POSTERLY_API_KEY": "YOUR_POSTERLY_API_KEY_HERE"
}
}
}
}
Frequently asked questions
Substack MCP is categorized under Social Media and uses a local stdio subprocess. Posterly belongs to Social Media and uses a local stdio subprocess. Pick Substack MCP for social media work and Posterly for social media.
Copy the mcpServers block from the config section on this page into your client's config (for example claude_desktop_config.json or ~/.cursor/mcp.json), then fully restart the client.
Substack MCP is listed as free. Auth: other. Posterly has no declared pricing — check the project's own site. If a server needs environment variables such as API keys, define them under the env key in your client's MCP config.
Yes. MCP clients support multiple servers: add conorbronsdon-substack-mcp and posterly-2 as separate keys in the same mcpServers object, and your assistant will call tools from either one.
On AllMCPs, Substack MCP has a quality signal of 68/100 (Great) with 6 views, 0 installs and 44 GitHub stars. Posterly has 63/100 (Good) with 1 views, 0 installs and 0 GitHub stars.