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

Beyond the annotations it discloses meaningful behavior: 'unavailable modes/conflicting inputs fail closed' (failure semantics) and 'same request_id replays the exact edit' (corroborating the idempotentHint with concrete replay semantics). It also clarifies that no payment/provider submit occurs, which is important for an agent reasoning about side effects on a WRITE tool.

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 tight sentences with the key fact ('Explicit WRITE') front-loaded, followed by scope exclusions and failure/idempotency behavior. No filler, though the phrasing is compressed enough that it verges on jargon-dense.

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?

For a mutation tool with no output schema and 5 required parameters, it covers scope, failure mode, and idempotency but omits what the call returns and the meaning of expected_rev and source_result_index, leaving an agent to infer concurrency and indexing semantics.

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 0%, so the description must compensate. It only covers request_id replay semantics and is silent on project_id, source_scene_id, target_scene_id, expected_rev (clearly an optimistic-concurrency revision), and source_result_index. This leaves most of the 6 parameters undocumented.

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 verb and resource are specific: it explicitly writes the last frame of a finished source scene plus a CAS graph connection into the target scene's first_frame slot. It is distinguishable from neighbours like materialize_last_frame or canvas_apply, though the dense jargon (CAS graph, verified first_frame slot) demands domain familiarity.

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?

It carves out scope with 'No payment or provider submit' and explains request_id replay, which helps an agent understand this is a graph-edit-only operation. However, it never names an alternative tool or states when to use this rather than materialize_last_frame, canvas_apply, or canvas_update_node.

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