css_fonts

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

With no annotations, the description carries the full burden. It correctly implies a read-only inspection via the verb 'Get', but does not disclose the return structure, whether the element must be rendered, or any potential failure modes. It adds value beyond the schema but leaves several behavioral aspects uncovered.

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 a single, tightly written sentence that front-loads the verb and resource, then clarifies with the parenthetical. Every word contributes, and there is no fluff.

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?

The tool is simple with one parameter, but there is no output schema and no mention of the return format (e.g., array of font names, objects with font details). The description explains what is retrieved but not what the tool actually returns, leaving a gap in contextual completeness.

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 coverage is 100% with the 'selector' parameter fully described in the input schema. The description adds no additional parameter semantics, so it rests at the baseline of 3.

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 uses the specific verb 'Get' with a clear resource ('actual fonts used to render an element') and adds a crucial distinction from just 'font-family'. This effectively differentiates it from sibling tools like css_computed_style and css_matched_rules, making the purpose unmistakable.

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 clearly implies the use case: when you need the actually loaded fonts rather than the declared font-family. It provides context but does not explicitly name alternatives or state when not to use this tool, falling short of a full 'when/when-not' guideline.

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