Check a flow before building it

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

Annotations already declare readOnlyHint=true and idempotentHint=true, so safety is covered. The description adds meaningful behavioral detail: it lists specific checks, notes that invalid flows silently save with 'NO CARD' or 'Unavailable', and admits its limitation ('cannot judge whether the flow does what the owner meant'). This enriches the annotation baseline without contradiction.

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 dense sentence, front-loaded with purpose and covering essential behavioral details. It is efficient with no filler. It could be slightly better structured (e.g., breaking into two sentences), but it is well within acceptable conciseness for the content provided.

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?

Given the complexity of the tool (nested objects, multiple flow parts) and the lack of an output schema, the description adequately covers what it does, why it is valuable, and its limitation. It does not describe the return value format, but that is not critical since the description explains what validation catches. The reasoning about the Homey's lenient acceptance provides sufficient context for correct usage.

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 the baseline is 3. The description does not add parameter-specific semantics beyond the schema; it focuses on the validation behavior. It does implicitly explain the structure (trigger, actions, conditions) through the checks, but not enough to raise the score above the baseline.

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 clearly states it 'checks a flow against this Homey without writing anything and without running anything' and enumerates specific validations: card existence/type, argument names/types, device/zone existence, and token references. This distinguishes it from flow creation/update tools by emphasizing it is a non-mutating validation step.

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 says 'Worth calling first, because the Homey itself accepts almost anything', providing clear when-to-use guidance. It implies using it before saving a flow, but does not explicitly name alternative tools or when not to use it. The sibling list includes flow_create/update, so context is strong but not stated.

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