vizcharter_update

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

With no annotations, the description carries the full behavioral burden and does so well: it specifies RFC 7386 merge-patch semantics (recursive object merge, null deletes, arrays replace), explains that replacement overrides patch, states that re-rendering and re-export happen to the same location, and lists the return value. This is transparent about side effects and semantics.

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?

Three dense sentences with no filler. The core purpose is front-loaded, followed by patch semantics, then side effects and return value. Every sentence adds information.

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 covers the operation, patch/replace semantics, destination of re-exports, and return value. With no output schema or annotations, this is a solid amount of context, though it omits potential failure modes or error behavior when lint findings are produced.

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 100%, so the baseline is 3, but the description adds real meaning beyond the schema by explaining how patch and replace behave and how they relate to each other. Format defaults are still only implied by the schema enum and not explicitly stated, but the added patch semantics justify a 4.

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 names the exact verb and resource ('Update an existing diagram from its .vizc.json source') and immediately distinguishes this from create/export siblings. The phrase 'existing diagram' plus the source file reference makes the tool's scope unmistakable.

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 clearly states this is for updating an existing diagram from its source file, which implies when to use it instead of create or export. However, it does not explicitly name alternative tools or state when not to use them, so it falls just short of full guidance.

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