Compose Preview Catalogs

ui_builder_branch_design

Fork a design at a revision into a branch to explore an alternative, or to change it without trampling somebody editing it live. A branch is a design with its own id: edit it with ui_builder_apply, look at it with ui_builder_view or ui_builder_get_design, compare it with ui_builder_diff_designs, then bring it back with ui_builder_merge_branch or drop it with ui_builder_archive_branch. Branch N times from the same revision to try N alternatives: merging one archives the others. Branches of a branch are refused; so are asset uploads, restores and document replacements on a branch. Needs write access to the design.

Input Schema

TableJSON Schema

Name	Required	Description
`name`	Yes	What this alternative is, e.g. `compact header`.
`token`	No	A grant token from poll_access, when you cannot set the X-Compose-Preview-Token header yourself — an MCP client fixes its headers at connect time, so this is how a token approved during this session is used in it. Prefer the header where you control it.
`branchId`	No	The branch's design id. Defaults to one minted from the parent's; naming one makes a retry idempotent.
`designId`	Yes	The design to branch.
`revision`	No	A retained revision to fork at. Omit for the current one.
`agentName`	No	Optional agent/client name shown to design viewers; self-reported.
`agentModel`	No	Optional current model name shown to design viewers; self-reported. Omit when unknown.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`branch`	Yes
`schema`	Yes
`summary`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 4, 2026

addedInput schema / properties / agentModel

Added value: +{
+  "description": "Optional current model name shown to design viewers; self-reported. Omit when unknown.",
+  "maxLength": 80,
+  "type": "string"
+}

addedInput schema / properties / agentName

Added value: +{
+  "description": "Optional agent/client name shown to design viewers; self-reported.",
+  "maxLength": 80,
+  "type": "string"
+}

AddedOct 1, 2026

TDQS

A4.4/5.0

Behavior5/5

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

With no annotations, the description carries the full burden and does so: write access is required, branches-of-branches and several mutation types are refused on a branch, merging one branch archives its siblings, and naming branchId makes a retry idempotent. This is exactly the operational context an agent needs before calling.

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?

Purpose and primary use case are front-loaded, and nearly every clause adds routing or constraint information rather than filler. It is dense and packs multiple constraints into single sentences, which slightly hurts scanability but wastes little.

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?

An output schema exists, so return values need not be explained. The description covers purpose, permissions, lifecycle routing, refusal cases and idempotency, leaving no significant gap for an agent deciding whether and how to call it.

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 description coverage is 100%, so the schema already documents all seven parameters including branchId idempotency and the token/header tradeoff. The description adds only the 'branch N times from the same revision' framing around the revision parameter, which is minimal beyond the schema baseline.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb, resource and precondition: 'Fork a design at a revision into a branch', with the branch defined as 'a design with its own id'. It routes to many siblings by role (apply, view, get_design, diff_designs, merge_branch, archive_branch), but never distinguishes itself from the close sibling ui_builder_fork_design, which an agent could easily confuse with this tool.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit when-to-use ('to explore an alternative, or to change it without trampling somebody editing it live'), names the alternatives for each subsequent step in the lifecycle, and states when-not via refusals (branch of a branch, asset uploads, restores, document replacements on a branch).

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

All Compose Preview Catalogs tools Inspect

Try in Browser

Shareable, User-Owned Context BackendPeople, applications, and agents read, write, and coordinate together in one context lake. Reach it over MCP, a CLI, a Python SDK, or REST.fulcradynamics.comAd

Glama MCP Gateway

Add one secure layer between your agents and this server.