buildonce.app — programmatic media platform

Integrations

BuildOnce MCP Server

BuildOnce provides a production-grade Model Context Protocol (MCP) server allowing AI agents like Claude to create, edit, organize, and render branded marketing templates directly from conversational chat interfaces.

Transport

Streamable HTTP

Modern POST streaming protocol

Authentication

OAuth 2.1 + PKCE

Dynamic client registration (RFC 7591)

Capabilities

31 MCP Tools

Templates, brand kit, render, assets, social

Server Endpoint URL

https://buildonce.app/v1/mcp

The MCP endpoint is OAuth-only. When connecting, your MCP client automatically discovers the OAuth endpoints and directs you to sign in and authorize the workspace on your behalf.

Guide

Connecting to Claude

BuildOnce integrates seamlessly with Claude via Claude.ai Custom Connectors or Claude Desktop.

Option A: Claude.ai Custom Connector

Connect BuildOnce directly inside Claude.ai web or mobile app (requires a Pro, Team, or Enterprise account):

Open your Claude.ai Account Settings (or Organization Admin Settings) and navigate to Connectors (or visit claude.ai/customize/connectors).

Click Add Custom Connector.

Enter the connector details:

Name: BuildOnce
Server URL: https://buildonce.app/v1/mcp

Click Connect. A pop-up window will open with BuildOnce's OAuth consent screen. Click Allow access to authorize Claude to interact with your workspace.

Claude Desktop uses the same Custom Connector flow as Claude.ai — open Settings → Connectors → Add custom connector inside the app and follow the same steps as above. BuildOnce's OAuth flow requires the connector UI; there is no supported hand-edited claude_desktop_config.json entry for it.

Try It Out in Claude

Once connected, ask Claude any of these prompts to test the integration:

Explore Library

"List all the templates in my BuildOnce workspace and show their tags and dimensions."

Apply Brand Kit

"Fetch my brand kit colors and fonts, and create a new 1080x1080 template for a Summer Sale."

Stock Photos

"Search for minimalist coffee shop photos on Unsplash to use in my new banner design."

Instant Render

"Render my latest template to a PNG and give me the download URL."

Developer Setup

Connecting Cursor & Other MCP Clients

Any MCP client supporting the 2024-11-05 / 2025-03-26 specification over HTTP can connect by specifying the server URL:

mcp.json

{
  "mcpServers": {
    "buildonce": {
      "url": "https://buildonce.app/v1/mcp"
    }
  }
}

Authentication

OAuth 2.1 Specification Details

BuildOnce adheres strictly to RFC 8414 (Authorization Server Metadata), RFC 9728 (OAuth 2.0 Protected Resource Metadata), and RFC 7591 (Dynamic Client Registration).

Authorization Server Metadata

https://buildonce.app/.well-known/oauth-authorization-server

Protected Resource Metadata

https://buildonce.app/.well-known/oauth-protected-resource

For full implementation details, visit the MCP OAuth API Reference.

Reference

All 31 Available Tools

Every tool is a first-class wrapper around BuildOnce services. Each tool contains declared annotations (readOnlyHint, destructiveHint, openWorldHint) compliant with Claude connector directory requirements.

Template Management

list_templates

List templates in the workspace with tags, description, dimensions, and per-page summaries.

Param	Type	Notes
search	string	Optional free-text search filter.
tags	string[]	Optional tag filter.
folderId	string	Filter by folder ID, or "root" for unfiled templates.
sort	string	Sort order for the results.
page	number	Page number (defaults to 1).
limit	number	Items per page (1–100).

get_template

Fetch a single template's metadata by its ID.

Param	Type	Notes
id*	string	Template public ID.

create_templatescope: template:write

Create a new template with one blank page of the given dimensions.

Param	Type	Notes
name*	string	Template name (1–120 chars).
description	string	Optional description (up to 500 chars).
tags	string[]	Up to 20 search tags.
width	number	Page width in pixels (1–20,000).
height	number	Page height in pixels (1–20,000).
folderId	string	Optional folder ID to file directly into.
pages	object[]	Start with your own pages instead of one blank page (up to 100).

update_templatescope: template:write

Rename, re-describe, or update tags on an existing template.

Param	Type	Notes
id*	string	Template public ID.
name	string	New template name.
description	string	New description.
tags	string[]	New tags array.

duplicate_templatescope: template:write

Make a complete copy of a template and its current draft canvas.

Param	Type	Notes
id*	string	Source template ID.
name	string	Optional name for the duplicate copy.

list_template_folders

List all organization folders in the workspace, with template counts.

move_templatescope: template:write

Move a template into a folder, or back to root (unfiled).

Param	Type	Notes
id*	string	Template ID.
folderId	string \| null	Target folder ID, or null for root.

Canvas Drafts, Versions & Variables

get_template_draft

Fetch a template's full editable canvas design document (Fabric.js pages, objects, layers).

Param	Type	Notes
id*	string	Template ID.
format	"compact" \| "full" \| "outline"	"compact" (default) omits default-valued properties; "outline" returns a lightweight per-layer summary for finding what to patch.
pageIds	string[]	Read only these pages (up to 100). The result is marked partial.
layerIds	string[]	Read only these layers (up to 500). The result is marked partial.
fields	string[]	Read only these layer properties (up to 50). id and type are always included.

save_template_draftscope: template:write

Replace a template's design document and automatically snapshot version history.

Param	Type	Notes
id*	string	Template ID.
design*	object	Full design JSON document ({ version, designName, pages }).
ifRevision*	number	The revision this save started from — fails with DRAFT_REVISION_CONFLICT if someone else saved since.

patch_template_draftscope: template:write

Edit part of a template's design without resending the whole document: change properties, add/remove/reorder layers, add/remove/resize pages.

Param	Type	Notes
id*	string	Template ID.
ifRevision*	number	The revision this patch started from — fails with DRAFT_REVISION_CONFLICT if someone else saved since.
ops*	object[]	Patch operations (set, remove, add, move, set_page, add_page, remove_page), applied in order, up to 200. set on a layer can carry animation fields, and set_page a page's duration and transition.
dryRun	boolean	Validate and report the result without saving.

list_template_versions

List the 10 most recent version snapshots of a template.

Param	Type	Notes
id*	string	Template ID.

get_template_version

Fetch an earlier version's design document to inspect before restoring.

Param	Type	Notes
id*	string	Template ID.
versionId*	string	Version ID.

restore_template_versionscope: template:write

Roll back a template to an earlier snapshot (creates an undo snapshot of the current state).

Param	Type	Notes
id*	string	Template ID.
versionId*	string	Version ID to restore.
ifRevision	number	Fail with DRAFT_REVISION_CONFLICT instead of replacing edits made since this revision.

list_template_parameters

List dynamic variable fields (text placeholders, image overrides) derived from canvas layers.

Param	Type	Notes
id*	string	Template ID.

Rendering & Output

render_templatescope: render:write

Render a template draft to PNG, JPEG or PDF, or the whole design as an animated MP4, WebM or GIF video, optionally applying variable modifications. A video costs 1 credit per started second (up to 60 s).

Param	Type	Notes
id*	string	Template ID.
format	"png" \| "jpeg" \| "pdf" \| "mp4" \| "webm" \| "gif"	Output file format (defaults to png). A video format renders every page as one video; if it is still rendering after about 20 seconds, the result is { renderId, status } — poll get_render.
modifications	Record<string, string>	Key-value variable overrides.
pageId	string	Specific page ID to render.
allPages	boolean	Render every page in the template.
preview	boolean	Free watermarked preview with per-layer layout info — check your work before a real render.
pageIds	string[]	Preview only — restrict to these pages (up to 12).
inline	"none" \| "thumbnail" \| "full"	How many page thumbnails to embed in the result (defaults to "thumbnail", the first 3 pages).
video	{ fps?, scale?, quality? }	Video only. fps 1–60 (GIF up to 15), scale 0.5 \| 1 \| 2, quality "small" \| "standard" \| "high".
at	number[]	Preview only — up to 12 moments, in seconds: a free sheet of the video's frames at those times, with the video's duration and price.
animation	{ pages?, layers? }	Change timing and animation for this render or preview only — different cuts of one template. Same shape as the render API's animation field.

get_renderscope: render:write

A render by renderId: status (queued, processing, succeeded or failed), its files and credits. Use it to wait for a video render_template returned as queued.

Param	Type	Notes
renderId*	string	The renderId from render_template.

Brand Kit & Stock Imagery

get_design_guide

The design guides. By default, the canvas guide: how a page.json is built — layer fields, text, images, shapes, variable bindings and limits. With topic: "animation", how to animate layers and pages for video: enter and exit presets, ambient motion, text reveals, page timing and transitions.

get_brand_kit

Fetch the workspace brand kit: logos (primary and dark-mode), brand fonts, color palette, and tone guidelines.

upload_assetscope: asset:write

Add a file to the workspace's media library and get back its id and a hosted URL. Used to fill the brand kit or add an image to a design from a brand brief.

Param	Type	Notes
kind*	"image" \| "font" \| "icon"	What kind of file is being uploaded.
url	string	A public http(s) URL for the server to download — pass this or base64, not both.
base64	string	The file's bytes as base64 (bare or a data: URL) — pass this or url, not both.
filename	string	Name for the stored file; for a font, also sets its font family.

update_brand_kitscope: asset:write

Save the workspace's brand: colors, logos, fonts and brand guidelines. Only the fields passed change. Requires the workspace admin role.

Param	Type	Notes
colors	object[]	Replaces the whole palette: { name, hex, role } entries.
primaryLogoAssetId	string \| null	Asset ID from upload_asset; null clears the logo.
reversedLogoAssetId	string \| null	Logo for dark backgrounds; null clears it.
fontAssetIds	string[]	Replaces the whole list of brand font asset IDs.
styleGuide	string	Freeform brand voice/guidelines text (up to 20,000 chars); "" clears it.

search_stock_photos

Search royalty-free stock photography from Pexels and Unsplash to inject into designs.

Param	Type	Notes
query	string	Search terms (e.g., "minimalist workspace").
provider	"pexels" \| "unsplash"	Filter by provider or omit for all.
page	number	Page number (defaults to 1).
perPage	number	Results per page (1–80).

Social Publishing

Render a design and post it in the same conversation. Accounts are connected on the dashboard's Social page; these tools post to the accounts already connected to the workspace. A post goes to a real account, so the agent confirms the account, text and media with you first.

get_platform_requirementsscope: social:read

Each platform's rules — character limit, required media, image or video, formats, which fields apply, platformOptions and delete support — from the same table posts are checked against.

Param	Type	Notes
platform	string	One platform, or omit for all.

list_social_accountsscope: social:read

List the social accounts connected to the workspace, with each one's platform, name and whether it needs reconnecting.

list_social_postsscope: social:read

List the workspace's posts, newest first, in every status — check whether a scheduled post went out or why one failed.

Param	Type	Notes
status / platform / accountId	string	Filters: status (scheduled, publishing, published, failed, canceled, deleted), platform, or one account.
from / to	string	ISO 8601 dates bounding when the post was created.
page	number	Page number (defaults to 1).
limit	number	Posts per page (1–100).

schedule_social_postscope: social:write

Schedule a post on one connected account; it publishes by itself at the scheduled time.

Param	Type	Notes
accountId*	string	Account ID from list_social_accounts.
content*	string	Post text (up to 3,000 characters).
mediaUrls	string[]	Up to 9 public image/video URLs — a render_template URL works as is.
linkUrl	string	Link to attach.
title / description / tags	string / string / string[]	LinkedIn and YouTube only.
accountIds	string[]	Post to several accounts at once instead of accountId — one result per account.
platformOptions	object	Per platform: instagram.postType (feed, story, reel), youtube.privacy / categoryId, pinterest.boardId, x.replyToPostId.
idempotencyKey	string	Sending the same key again returns the original post instead of posting twice.
dryRun	boolean	Check the post against the platform's rules and return valid, errors and warnings — nothing is created or posted.
scheduledAt*	string	ISO 8601 with a timezone, e.g. "2026-10-08T09:00:00+05:00". Must be in the future.

publish_social_postscope: social:write

Publish a post on one connected account right now. Returns published, or failed with the reason.

Param	Type	Notes
accountId*	string	Account ID from list_social_accounts.
content*	string	Post text (up to 3,000 characters).
mediaUrls	string[]	Up to 9 public image/video URLs — a render_template URL works as is.
linkUrl	string	Link to attach.
title / description / tags	string / string / string[]	LinkedIn and YouTube only.
accountIds	string[]	Post to several accounts at once instead of accountId — one result per account.
platformOptions	object	Per platform: instagram.postType (feed, story, reel), youtube.privacy / categoryId, pinterest.boardId, x.replyToPostId.
idempotencyKey	string	Sending the same key again returns the original post instead of posting twice.
dryRun	boolean	Check the post against the platform's rules and return valid, errors and warnings — nothing is created or posted.

get_social_postscope: social:read

One post by ID, in full — status, lastError, externalPostId, publishedAt. Poll it after publishing a video.

Param	Type	Notes
postId*	string	Post ID.

update_scheduled_postscope: social:write

Change a scheduled post's text, media, link or time, keeping the same ID. Checked like a new post.

Param	Type	Notes
postId*	string	A post that is still scheduled.
content / mediaUrls / linkUrl / scheduledAt …	optional	Only the fields that change.

retry_social_postscope: social:write

Publish a failed post again as the same post. Refused with RETRY_UNSAFE when the first attempt may already be live (it timed out or was interrupted).

Param	Type	Notes
postId*	string	A post with status failed.

delete_social_postscope: social:write

Remove a published post from its platform. Works on X, Facebook, LinkedIn, Pinterest, Discord and Bluesky; Instagram, TikTok, Threads and YouTube return unsupported_by_platform with the reason.

Param	Type	Notes
postId*	string	A published post.
confirm*	true	Required — deleting is permanent.

cancel_social_postscope: social:write

Cancel a scheduled post before it goes out. A post already sent can't be canceled.

Param	Type	Notes
postId*	string	Post ID from schedule_social_post or list_social_posts.

Was this page helpful?