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

With no annotations provided, the description carries the full burden, and it delivers: it discloses rejection of built-in families, the deduplication/replacement behavior by family+weight+style, the lack of verification that an uploaded filename exists, and the CORS limitation for pasted URLs. These are meaningful behavioral traits beyond what the schema alone reveals.

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?

The description is dense but every sentence earns its place: purpose, rejection rule, src formats, caveats, dedupe behavior, and follow-up usage. It is front-loaded with the core purpose and never wastes words.

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?

For a mutation tool with 5 parameters and no output schema, the description covers prerequisites, input alternatives, behavioral side effects, failure-prone scenarios (CORS, unverified filenames), and post-registration usage. An agent has enough to select and invoke this tool correctly without needing additional external context.

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?

Although schema description coverage is 100%, the description adds critical semantics beyond it: src is elaborated as either a full URL or an uploaded asset with upload endpoint details, family is tied to how text layers reference it, and weight/style are implied in the dedupe-by-family+weight+style behavior. This materially enriches parameter understanding.

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?

The description opens with a specific verb+resource: 'Register a typeface Morpha does NOT ship, so text layers can use it by family name via font_family.' It clearly differentiates this from simply setting a font_family on built-in fonts, and the distinction from list_fonts is implicit in the rejection of built-in catalog families.

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 explicitly states when to use the tool: for typefaces Morpha does not ship, and when not to: built-in catalog families are rejected and should be referenced directly via font_family. It also names the follow-up actions (add_text_layer / set_layer_text), the alternative upload path, and the CORS caveat that makes upload the robust choice.

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