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

Adds real behavior beyond the annotations: it is idempotent (skips typefaces with existing files or no family), additive-only ('changes nothing else'), reaches an external source (consistent with openWorldHint), and reports back typefaces Google lacks. This clarifies the non-destructive nature and the failure path in ways annotations alone (readOnlyHint=false, destructiveHint=false) do not.

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?

Four sentences, front-loaded with the core action and benefit, then the fetch condition, scope, and failure handling. No filler, though it is mildly wordy and could tighten the first sentence.

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 no output schema and full schema coverage, the description supplies the missing pieces: what gets added, what is left untouched, idempotency, and the not-found path with an upload remedy. Safety is covered by annotations, so remaining gaps are minor.

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 kitId and workspace semantics are already fully documented in the schema. The description restates the kit/workspace scope but adds no format or edge-case detail beyond what the schema provides. Baseline 3 applies when the schema does the heavy lifting.

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 and resource: fetches a kit's typeface font files from Google Fonts and stores them in the kit. The effect (decks, slides and canvas render the real brand typefaces) makes the purpose concrete. It does not explicitly name the sibling it differs from (e.g. napkin_brand_add_files), though the upload fallback hints at the boundary.

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?

Implies usage via scope ('Works on any kit, including the workspace's brand') and a fetch condition ('only typefaces that name a family and don't have files yet are fetched'), which tells the agent when the call is a useful/likely no-op. However, it never states when to call this versus napkin_brand_add_files or other brand tools, so selection guidance is inferred rather than explicit.

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