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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so safety and idempotency are fully covered structurally. The only behavioral fact the description adds is 'Cost: Free', which is genuinely useful and not in the annotations, but it says nothing about whether fonts are project-scoped vs global, whether a font must exist to be used, or any limits.

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?

Two short sentences with zero padding, so nothing is wasteful, but the brevity comes at the cost of under-specification rather than efficiency. The most important information — that this returns the list of usable fonts — is absent, so the fragment does not lead with the action.

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 need not be described, and with no parameters the surface is small. Even so, a definition that never states the tool lists available fonts, and never says these fonts are what set_captions/write_graphic consume, leaves a real gap for a discovery-type tool surrounded by font-relevant siblings.

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?

The tool takes zero parameters, so the baseline is 4; there is no parameter semantics to explain. The description does not need to compensate for any schema gap here.

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 title says 'List the fonts' and the name says get_font_family_info, but the description itself ('Fonts for captions, overlays, and graphics. Cost: Free.') never says what the tool does — no verb, no statement that it returns the available font families. It labels a content category and a price, which is close to restating the title rather than defining the operation. An agent must infer 'lists fonts' from the name/title alone.

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?

There is no when-to-use guidance, no prerequisites, and no routing to alternatives among the many siblings such as browse_styles, set_captions, or write_graphic. 'For captions, overlays, and graphics' gestures at applicable contexts but does not tell the agent to call this before set_captions or write_graphic when it needs a valid font identifier.

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