set_arc

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

Annotations only signal readOnlyHint=false and destructiveHint=false, so the description carries the behavioral burden. It explains how angles carve the wedge, what innerRadius does (0=solid disc, >0=ring), and that updates are partial. It also states the return value { ok, nodeId }. This adds meaningful detail without contradicting annotations.

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 two sentences: the first states the purpose and includes value explanations, the second covers constraints and return value. Every clause adds necessary context, and the most important information is front-loaded. There is no redundancy or filler.

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?

The description fully covers the tool's input semantics (units, ranges, node type restriction), update behavior (partial updates), and output (return shape). The schema and annotations handle structured details, and the description fills in the behavioral and interpretive gaps. No significant missing context for an agent to invoke the tool correctly.

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?

The schema already has 100% parameter descriptions, but the description adds concrete numeric anchors (full circle is 0 → 2π ≈ 6.28319, half is π ≈ 3.14159) and clarifies innerRadius as '0–1 of the radius' with a donut example (0.6). It also explains that all fields are optional except nodeId, and that omitted fields retain current values. This goes beyond the schema's basic type/range info.

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 opens with a specific verb+resource combination: 'Turn an ellipse into a pie slice / gauge or a ring / donut by setting its arc data.' This clearly states the tool's function and differentiates it from sibling tools like set_fills or set_strokes, which target other visual properties.

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?

The description explicitly notes 'Only ellipses have arc data,' telling the agent when this tool applies. It also explains the subset-update semantics ('Pass any subset — omitted fields keep their current value. At least one is required.'), which guides usage. It doesn't mention explicit alternatives, but the context is clear enough for selecting this tool over other setter tools.

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