set_fill_parameters

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

With no annotations, the description carries the full burden; it does add one genuinely valuable behavioral trait — atomic 'rolls back on failure'. But critical mutation semantics are absent: whether the `values` object is merged into or replaces existing parameters, what happens to unspecified parameters, and whether the operation requires specific permissions or an open project.

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?

A single tight sentence with the destructive/atomic behavior front-loaded after the purpose — no filler. Brevity is efficient, though it edges toward under-specification rather than crispness.

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 a free-form nested payload, zero schema descriptions, and no annotations, the definition leaves too much open: valid parameter keys, merge-vs-replace behavior, and channel targeting are all unstated. The output schema does cover return values, so that need is satisfied, but the invocation contract is not.

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% across 3 parameters, and `values` is an unconstrained nested object (additionalProperties: true) — the exact case where the description must compensate. It says nothing about which keys are valid in `values`, what format they take, or what `channel` selects when omitted, leaving the agent to guess at the call shape.

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 ('Update parameters') and enumerates the target resource types (Fill, Fill Effect, Generator, Filter), which is far more precise than a bare name restatement. However, it never distinguishes itself from close siblings like set_fill_base_color, set_fill_channels, set_procedural_input, or apply_fill_preset, so the agent must infer the boundary.

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?

Usage is only implied by the object types it targets; there is no explicit 'use this when...' guidance, no mention of prerequisites (layer/fill must exist), and no routing to alternatives such as set_procedural_input for procedural inputs. An agent can guess, but with 4 similarly-named set_fill_* siblings the omission matters.

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