Icon Generate

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

Annotations already declare openWorldHint=true, readOnlyHint=false, destructiveHint=false. The description adds real value beyond that: the operation is paid, opt-in only, gated by a refusal unless allow_external_generator is true, and writes to a draft directory rather than installing. It stops short of noting rate limits or cost magnitude, keeping it at 4 rather than 5.

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?

Dense and front-loaded: purpose first, then the routing rule, then the return/refusal contract. Three compact sentences with no filler, though the parenthetical '(paid, opt-in only)' mildly duplicates the later refusal clause.

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, yet the description still summarizes the return contract ({ok, draft, prompt, next} or refusal) and covers the gating, destination, and relationship to icon_install. Nothing an agent needs to call this paid external generator correctly is missing.

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 app_dir, concept, extra, and allow_external_generator are already documented, including the default-false refusal semantics. The description restates the refusal gate but adds no new syntax or format detail. Baseline 3 is correct 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+resource+engine: generate a fal.ai raster icon DRAFT into design/icon_drafts/. It explicitly distinguishes itself from the sibling icon_install by noting it never installs an icon. An agent can tell these two apart without opening either schema.

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?

Gives an explicit 'Use when' condition (the user explicitly allows an external generator), states the alternative (icon_install for the shipped icon), and names the gate (allow_external_generator=true). When-to-use, when-not, and the alternative are all present.

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