Compose Preview Catalogs

ui_builder_set_links

Say what a design is for. Replaces the whole record: send every link you want kept, and omit one to clear it — so read ui_builder_get_links first if you are adding to what is already there. issue, reference, pr and thread are absolute http or https URLs, at most 2 KB each; previous is a design id on this host, not a URL. Anything else is refused with the reason. Sending an empty record clears it. Record the pr when you open one for a design you built here: it is what lets the next session, and the person who filed the issue, find one from the other.

Input Schema

TableJSON Schema

Name	Required	Description
`pr`	No	The pull request that implemented it.
`issue`	No	The tracker issue this design is for.
`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.
`thread`	No	A permalink to a discussion held elsewhere, such as a chat thread. It does not replace this server's comments for a server-homed design: keep that discussion on the design.
`designId`	Yes
`previous`	No	The design id on this host that this one continues.
`agentName`	No	Optional agent/client name shown to design viewers; self-reported.
`reference`	No	The frame in the design tool it reproduces.
`agentModel`	No	Optional current model name shown to design viewers; self-reported. Omit when unknown.

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

A4.2/5.0

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 well: it discloses destructive replace-whole-record semantics, that omission clears a field, that an empty record clears everything, per-field validation (absolute http/https URLs, 2 KB max, `previous` must be a design id not a URL), and that invalid input is refused with a reason. This is exactly the behavioral context an agent needs before a mutating call.

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?

Densely informative and front-loaded with the most important fact (whole-record replacement) before the field rules. The closing sentence about recording `pr` is rationale rather than instruction and runs slightly long, but it is short of padding.

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?

For a 9-parameter mutation tool with an output schema, the description covers replacement semantics, validation, clearing behavior, and the read-before-write workflow; return values need not be explained. Only the identity parameters are absent, and the schema handles those, so it is complete enough to invoke correctly.

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 89%, so the baseline is 3, but the description adds genuine meaning the schema lacks: format and size constraints on `issue`/`reference`/`pr`/`thread`, and the critical distinction that `previous` is a host-local design id rather than a URL. Auth/identity params (`token`, `agentName`, `agentModel`) are left to the schema, which documents them adequately.

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?

The description states a specific verb+resource (setting the link record for a design) and disambiguates from the get_links sibling by naming it explicitly. The opening line 'Say what a design is for' is somewhat abstract, but the immediately following sentence pins down the operation precisely.

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

Usage Guidelines4/5

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

It gives a concrete precondition and routing rule: read ui_builder_get_links first when adding to an existing record, and explicitly explains when to send an empty record. It also advises recording `pr` at the moment you open one. There is no explicit when-not-to-use beyond that, but the conditions that select this tool are clear.

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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