Font Design MCP

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font_build

Build real TTF and/or WOFF2 from a frozen revision, automatically variable when axes/masters are configured. Returns persistent relative paths and hashes without altering sources.

Instructions

Build real TTF and/or WOFF2 from a frozen revision, automatically variable when axes/masters are configured. Returns persistent relative paths and hashes. Does not alter sources.

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": {
      "project_id": "<project_id>"
    },
    "name": "font_build"
  }
}

Input Schema

Name	Required	Default
`formats`	No
`purpose`	No	proof
`revision`	No
`project_id`	Yes
`review_uris`	No
`require_design_checks`	No

Output Schema

Name	Required	Description	Default
`ok`	Yes
`data`	No
`error`	No
`changed`	No
`summary`	Yes
`revision`	No
`warnings`	No
`project_id`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv0.6.0Sep 12, 2026

addedInput schema / properties / purpose

Added value: +{
+  "default": "proof",
+  "enum": [
+    "proof",
+    "release"
+  ],
+  "type": "string"
+}

addedInput schema / properties / review_uris

Added value: +{
+  "items": {
+    "maxLength": 250,
+    "type": "string"
+  },
+  "maxItems": 128,
+  "type": "array"
+}

Changed1 schema field changedv0.5.0Sep 10, 2026
- addedInput schema / properties / require_design_checks
```
Added value: +{
+  "default": false,
+  "type": "boolean"
+}
```
Changed13 schema fields changedv0.4.3Sep 9, 2026
- removedInput schema / properties / formats / title
```
Removed value: -"Formats"
```
- removedInput schema / properties / project_id / title
```
Removed value: -"Project Id"
```
- removedInput schema / properties / revision / title
```
Removed value: -"Revision"
```
- removedInput schema / title
```
Removed value: -"Build"
```
- removedOutput schema / properties / changed / title
```
Removed value: -"Changed"
```
- removedOutput schema / properties / data / title
```
Removed value: -"Data"
```
- removedOutput schema / properties / error / title
```
Removed value: -"Error"
```
- removedOutput schema / properties / ok / title
```
Removed value: -"Ok"
```
- removedOutput schema / properties / project_id / title
```
Removed value: -"Project Id"
```
- removedOutput schema / properties / revision / title
```
Removed value: -"Revision"
```
- removedOutput schema / properties / summary / title
```
Removed value: -"Summary"
```
- removedOutput schema / properties / warnings / title
```
Removed value: -"Warnings"
```
- removedOutput schema / title
```
Removed value: -"Result"
```
First observedv0.1.0Sep 8, 2026

TDQS

B3.1/5.0

Behavior3/5

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

Annotations declare readOnlyHint=false and destructiveHint=false, so the mutation profile is known. The description adds useful context ('Does not alter sources', 'Returns persistent relative paths and hashes', automatic variable output), but omits whether builds are cached, whether they overwrite existing artifacts, or any auth/permission requirements. Given annotations cover the safety profile, this additional context earns a middle score.

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 tightly packed sentences with no filler, front-loading the core action and then the behavioral guarantees. Every clause supplies information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return-value explanation is unnecessary. However, for a 6-parameter, mutation-performing build tool with 0% schema description coverage, the absence of parameter-level guidance (especially purpose and the check/review options) leaves the agent under-informed.

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

Parameters2/5

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

Schema description coverage is 0%, so the description must carry the burden for 6 parameters. It mentions formats implicitly ('TTF and/or WOFF2') and the revision source ('from a frozen revision'), but does not explain purpose (proof vs release), require_design_checks, review_uris, or project_id. It leaves most parameters undocumented.

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: building real TTF/WOFF2 from a frozen revision, and notes automatic variable output when axes/masters are configured. Does not explicitly distinguish itself from font_release_check or font_validate siblings, but the build output (font binaries) is clearly distinct.

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?

No when-to-use or when-not-to-use guidance. There is no mention of alternatives such as font_release_check or font_validate, nor any indication of when a 'proof' vs 'release' build should be performed despite that distinction existing in the schema.

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