List style targets for a block type

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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint, openWorldHint), so the bar is lower. The description still adds real value beyond them: it declares 'makes no call to Home Assistant,' that the lookup is against an embedded schema, the exact return shape, and the error contract. Only minor gaps (e.g. whether unknown types fall back to 'block') remain.

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-loads the core purpose in the first sentence, then uses compact labeled clauses (Use when / Returns / Errors) to add only actionable detail. No filler sentences and nothing wasted.

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?

Covers purpose, usage condition, a concrete example, the return object, and the error shape. An output schema exists so return values need not be repeated, and the description is still complete for a one-parameter read tool.

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 single parameter is fully documented in the schema, so the baseline is 3. The description adds only a redundant example value ('block-entity-field-state') and clarifies that the value originates from card_builder_list_block_types, which the schema already states.

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 and resource ('List the style targets (sub-components) one block type supports') and immediately clarifies the internal mechanism via the STYLE_TARGETS lookup. An agent can distinguish this from sibling card_builder_list_block_types and card_builder_build_styles without opening any 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?

Explicitly states 'Use when: styling a sub-component of a block (e.g. a slider's thumb) rather than the whole block,' which gives clear context and a contrast with the whole-block case. It does not name a specific sibling tool as the alternative, so it falls just short of the 5-tier 'when/when-not/alternatives' bar.

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