Font Design MCP

Overview Schema Source Related Servers Discussions Admin

spacing_edit

Set font advances, side bearings, and kerning pairs or groups on a master. Applies spacing changes atomically, moving outlines for bearings while keeping advances fixed.

Instructions

Atomically set advances, side bearings, kerning groups or pairs in master_id (default: 'default'). Bearings move outlines; advances do not.

Input Schema

TableJSON Schema

Name	Required	Default
`summary`	No
`master_id`	No	default
`operations`	Yes
`project_id`	Yes
`expected_revision`	Yes

Output Schema

TableJSON 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.

Changed33 schema fields changedv0.4.3Sep 9, 2026
- removedInput schema / $defs / Bearings / properties / glyph_id / title
```
Removed value: -"Glyph Id"
```
- removedInput schema / $defs / Bearings / properties / left / title
```
Removed value: -"Left"
```
- removedInput schema / $defs / Bearings / properties / op / title
```
Removed value: -"Op"
```
- removedInput schema / $defs / Bearings / properties / right / title
```
Removed value: -"Right"
```
- removedInput schema / $defs / Bearings / title
```
Removed value: -"Bearings"
```
- removedInput schema / $defs / KernGroup / properties / glyphs / title
```
Removed value: -"Glyphs"
```
- removedInput schema / $defs / KernGroup / properties / name / title
```
Removed value: -"Name"
```
- removedInput schema / $defs / KernGroup / properties / op / title
```
Removed value: -"Op"
```
- removedInput schema / $defs / KernGroup / title
```
Removed value: -"KernGroup"
```
- removedInput schema / $defs / KernPair / properties / left / title
```
Removed value: -"Left"
```
- removedInput schema / $defs / KernPair / properties / op / title
```
Removed value: -"Op"
```
- removedInput schema / $defs / KernPair / properties / right / title
```
Removed value: -"Right"
```
- removedInput schema / $defs / KernPair / properties / value / title
```
Removed value: -"Value"
```
- removedInput schema / $defs / KernPair / title
```
Removed value: -"KernPair"
```
- removedInput schema / $defs / SetAdvance / properties / glyph_id / title
```
Removed value: -"Glyph Id"
```
- removedInput schema / $defs / SetAdvance / properties / op / title
```
Removed value: -"Op"
```
- removedInput schema / $defs / SetAdvance / properties / value / title
```
Removed value: -"Value"
```
- removedInput schema / $defs / SetAdvance / title
```
Removed value: -"SetAdvance"
```
- removedInput schema / properties / expected_revision / title
```
Removed value: -"Expected Revision"
```
- addedInput schema / properties / master_id
```
Added value: +{
+  "default": "default",
+  "pattern": "^[a-zA-Z0-9_][a-zA-Z0-9_.-]{0,63}$",
+  "type": "string"
+}
```
- removedInput schema / properties / operations / title
```
Removed value: -"Operations"
```
- removedInput schema / properties / project_id / title
```
Removed value: -"Project Id"
```
- removedInput schema / properties / summary / title
```
Removed value: -"Summary"
```
- removedInput schema / title
```
Removed value: -"SpacingEdit"
```
- 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

A3.8/5.0

Behavior4/5

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

Annotations already indicate a non-read-only, non-idempotent mutation. The description adds two valuable behavioral details: atomicity (all-or-nothing) and the distinction that bearings move outlines while advances do not. This goes beyond the annotations without contradicting them.

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?

The description is concise (two sentences) and front-loads the atomicity and scope. The key behavioral distinction is delivered efficiently without redundancy.

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?

For a tool with four operation types and atomic semantics, the description covers the core purpose and one behavioral nuance but omits details like batching behavior, the role of expected_revision (optimistic locking), and failure handling. The output schema may clarify return values, but the description itself leaves gaps for a complex mutation tool.

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 compensate. It only names the four operation types (advances, bearings, kern pairs/groups) but does not explain fields like 'left', 'right', 'value', or 'glyph_id'. The schema itself provides no descriptions, leaving the agent to infer field meanings from names alone.

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?

The description clearly states the tool's action ('Atomically set') and resources (advances, side bearings, kerning groups or pairs). It also specifies the default master_id, making the purpose unambiguous and distinct from sibling editing tools.

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

Usage Guidelines3/5

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

The description implies usage for spacing adjustments but does not explicitly compare with alternatives like glyph_edit or font_edit, nor does it state when not to use this tool. There is no exclusion or routing guidance.

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