Retrieve detailed metrics for a registered font—including ascender, descender, xHeight, capHeight, available weights, and kerning pair count—to inform generative art layouts.
Return detailed metrics for a registered font: ascender, descender, xHeight, capHeight, available weights, and kerning pair count.
| Name | Required | Description | Default |
|---|---|---|---|
| weight | No | Specific weight to query (default: 400). | |
| fontFamily | Yes | Font family name. |
Changes observed during successful MCP inspections.
v0.5.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations exist, so the description carries full burden; 'Return' implies a safe read, and it usefully discloses the exact payload fields (ascender, descender, xHeight, capHeight, weights, kerning pair count). It omits what happens for an unregistered font family, the units of the metric values, and whether an explicit weight changes only the reported weight metadata or the metric values themselves.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
A single front-loaded sentence with the payload enumeration inline; every clause earns its place and there is no filler.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With only two parameters, full schema coverage, and no output schema, listing the returned fields in the description is exactly the right compensation. Only the absence of unit/error behavior keeps it from being fully complete.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so both parameters (fontFamily, weight with default 400) are already documented in the schema; baseline 3 applies. The description adds nothing about the weight parameter's effect on results, and 'available weights' refers to returned data rather than the input parameter, which could mildly confuse.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb (Return) plus resource (detailed metrics for a registered font) and enumerates exactly which metrics come back, which clearly separates it from listing tools like design_list_fonts. It stops short of naming any sibling or stating the register-font prerequisite explicitly, so it is clear but not maximally differentiated.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description never says when to call this versus design_list_fonts, design_load_custom_font, or design_analyze_text_spacing, and gives no prerequisites beyond the incidental word 'registered'. The agent must infer the trigger condition and the requirement that the font already be registered.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.