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

Annotations cover the safety profile (readOnly, openWorld, idempotent=false, destructive=false), and the description adds substantial context beyond them: free/read-only, catalog contents (family + category + variants + css2 URL), the silent fallback to Liberation Sans with no error, and the ambiguity of an empty result. This is information an agent cannot get 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.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with purpose and usage, with the critical fallback caveat marked IMPORTANT. It is dense and nearly every sentence carries operational value, though the parenthetical detail about catalog fields slows the read slightly.

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?

An output schema exists so return values needn't be spelled out, yet the description still characterizes the shape (family/category/variants/css2 URL) and, crucially, warns about the misleading nature of results. Complete for this tool's complexity and its high-stakes naming trap.

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% and the keys are already constrained (query minLength 1/maxLength 200, perPage ≤50), so the description's 'Pass query (+ optional perPage ≤50)' largely restates the schema. Baseline 3 for full schema coverage; no additional format or query-syntax semantics are added.

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?

Specific verb+resource ('Search web font families by name/style') with an explicit statement of what it returns and how the result is used. It also distinguishes itself from the sibling list_render_fonts by declaring that this is the Google catalog, not the selectable render set.

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?

Explicitly routes the agent: use list_render_fonts for the set you may actually choose from, and treat that, not this catalog, as the list. It also explains why (non-vendored faces silently fall back) and what an empty result means, covering when-not and alternatives.

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