CueFrame

List Render Fonts

list_render_fonts

Read-only

The fonts the RENDERER can actually draw — read this BEFORE authoring type, not after a refusal. Per family: the exact family name authoring accepts, the weight RANGES a shipped file declares (a static face has min===max; a variable face gives its axis range), the caption default weights, and whether the bytes are bundled or an aliased metric-compatible stand-in. Anything listed here passes validation by construction: it is derived from the same table the font gate refuses by. Two facts worth reading off it — every family's styles is ["normal"], because NO bundled family ships an italic FILE (a real italic comes only from a brand-kit font asset), and a weight outside every range is REFUSED, never synthesised. Contrast search_fonts, which searches the GOOGLE catalog and will happily return families the renderer cannot draw. manifestVersion identifies this exact face table; record it beside a composition to state what a font choice was validated against. Covers the bundled set only — a brand kit's sealed faces are per-org and per-render. No args, read-only, free.

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Output Schema

TableJSON Schema

Name	Required	Description	Default
`families`	No
`manifestVersion`	No	Identifies this exact face table. Derived from the table's own content, so it moves when and only when the admitted set moves. Record it beside a composition to state which face table a font choice was validated against.

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 10, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Annotations cover read-only/open-world status, but the description adds real substance beyond them: results pass validation by construction (same table the font gate refuses by), every family's styles is ['normal'] because no bundled italic files ship, out-of-range weights are refused rather than synthesised, and the bundled-only scope excludes brand-kit faces. These are non-obvious behavioral facts an agent cannot infer from the schema.

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?

Purpose and the search_fonts contrast are front-loaded, and the setup guidance precedes the field explanations. It is dense and largely earns its length, though the prose is heavier than strictly necessary for a no-arg list tool.

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?

An output schema exists, yet the description still frames what the result means operationally (validation-by-construction, manifestVersion as a provenance record, brand-kit exclusion). Combined with the usage routing, an agent has everything needed to call it 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?

There are zero parameters, so the baseline is 4. The description instead describes the returned fields (family name, weight ranges with static min===max semantics, caption defaults, bundled vs aliased bytes), which is useful but belongs to output rather than parameter semantics.

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 verb and resource ('the fonts the RENDERER can actually draw') and immediately contrasts it with the sibling search_fonts, which returns Google-catalog families the renderer cannot draw. An agent can distinguish the two without opening either 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?

Explicitly says to read it 'BEFORE authoring type, not after a refusal', and names the alternative (search_fonts) plus the condition that separates them. When-to-use and when-not-to-use are both stated.

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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