Compose Preview Catalogs

ui_builder_await_comments

Wait for the discussion to move past afterSequence and return it, rather than polling for it. Returns as soon as anybody — a designer in the browser or another agent — posts, resolves or deletes; returns a timedOut reply if nothing happens within waitSeconds, which you answer by calling again with the same cursor. This is how you hold a conversation about a design: post, wait, read, act.

Input Schema

TableJSON 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.
`designId`	Yes
`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.
`waitSeconds`	No	Up to 120. Defaults to 25.
`afterSequence`	Yes	The `sequence` you last saw. 0 for anything at all.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

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"
+}

Changed1 schema field changedSep 30, 2026
- changedOutput schema / (root)
```
Previous value: -nullNew value: +{
+  "type": "object"
+}
```
First observedSep 30, 2026

TDQS

A4.9/5.0

Behavior5/5

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

No annotations exist, so the description carries the full burden, and it delivers: it discloses what wakes the call (a post, resolve or delete by anyone — designer or agent), the timeout output name (`timedOut`) and its bound (`waitSeconds`), and the required retry semantics. Auth/token handling is covered by the schema's own token description.

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 tight sentences: the operation, the wake/timeout behavior, then the conversational framing. The core behavior is front-loaded and no sentence is wasted.

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?

With an output schema present, return-format detail isn't required, yet the description still explains the one output that matters for control flow (timedOut) and how to respond to it. Nothing an agent needs to call and continue the conversation is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is already 83%, so the baseline is 3, but the description adds real meaning: `afterSequence` is framed as a cursor ('the discussion to move past'), and `waitSeconds` is tied to the timedOut reply and the re-call-with-same-cursor rule. Only the optional token/agentName/agentModel params are left to the schema.

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 action (wait for the discussion to move past a cursor and return it) and explicitly contrasts with the alternative behavior (polling). An agent can distinguish this from siblings like ui_builder_list_comments or ui_builder_await_decision without opening any schema.

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 the exact usage loop — 'post, wait, read, act' — and states when to call again (after a timedOut reply, with the same cursor). It also names the pattern it replaces ('rather than polling'), which is the key decision point against sibling tools.

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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