Compose Preview Catalogs

ui_builder_list_branches

A design's branches, newest first: each one's id, name, owner, status (open, merged, archived), fork revision, head revision and the number of commands a merge would replay; for a merged one the parent revision it landed at, for an archived sibling the branch whose merge superseded it. Read access to the design.

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": {
      "designId": "<designId>"
    },
    "name": "ui_builder_list_branches"
  }
}

Input Schema

Name	Required	Description
`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.
`status`	No	Only branches in this state. Defaults to all.
`designId`	Yes	The parent design.
`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

Name	Required	Description	Default
`schema`	Yes
`status`	Yes
`summary`	Yes
`branches`	Yes
`designId`	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

B3.2/5.0

Behavior3/5

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

With no annotations, the description carries the full burden. It usefully discloses read-only access ('Read access to the design') and the ordering guarantee ('newest first'), plus per-field semantics for merged/archived branches, but says nothing about pagination, result limits, or what happens with large branch sets.

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?

Two sentences, front-loaded with the resource and its ordering, with zero filler. The long field enumeration is somewhat redundant given an output schema exists, but it is tightly written and scannable.

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?

An output schema covers return values and the schema covers all parameters, so the description's job is scope, ordering, and access — all of which it supplies. Only pagination/volume behavior is left unstated for a moderate-complexity read tool.

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 all five parameters are already documented, including the token/agentName/agentModel fields. The description adds no parameter-level syntax or defaults beyond the schema, so the baseline 3 applies.

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?

Names a specific verb+resource ('a design's branches') and enumerates the returned fields, so the agent knows exactly what is being listed. It does not explicitly contrast with near neighbors such as ui_builder_list_revisions or ui_builder_compare_branches, but the 'branches of one design' framing is unambiguous.

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

Usage Guidelines2/5

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

There is no when-to-use or when-not-to-use guidance and no alternative tool is named; the agent must infer from the sibling list that list_revisions/compare_branches are different operations. Only the trailing 'Read access to the design' hints at a precondition.

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

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