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

Annotations already cover read-only/idempotent safety, and the description adds genuinely new behavior: up to three image previews of affected frames and the caveat that images may be unavailable. It also notes legacy test support, which is not derivable from the schema.

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?

Four tight sentences that front-load the read operation and the ID dependency, then add the image-preview caveat. No filler, though the 'Legacy tests also supported' clause is appended somewhat abruptly.

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 explained, and the description still flags the unreliable image previews. The main gap is that testId, a required parameter, is never addressed.

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 only 25%, so the description must compensate. It explains scId's source, ties runId/blockId to list_test_blocks, and covers blockId omission semantics, but the required testId is never explained in the description and runId's role is only implied.

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 ('Read') and resource ('accessibility criterion and its evidence'), and ties the scId to list_success_criteria. It does not explicitly contrast itself with nearby siblings like get_insight or list_success_criteria, but the resource is unambiguous.

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 routes the agent to list_success_criteria for scId and list_test_blocks for block/run targeting, and notes that omission falls back to documented defaults. No when-not-to-use guidance, but the context is clear.

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