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

Annotations already declare readOnly=false, so mutation is known. The description adds state-changing behavior ('Changes the chart you are building') and a workflow expectation (call chart_link), which is useful beyond annotations. No contradictions.

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 tight sentences, front-loaded with purpose, followed by usage context, then workflow. No 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?

For a 16-parameter mutation tool with no output schema, the description covers the core workflow (id source, purpose, final link) but leaves many parameter semantics to an incomplete schema. An agent can call it, but incomplete parameter documentation is a gap.

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 56%, and the tool description does not compensate: it only repeats id source ('from chart_state') and advises on colour usage. Several parameters (lineStyle, showStats, arrowStart/End, extendLeft/Right, showLabels) remain undocumented in both schema and description.

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 clear verb+resource ('Change how an existing drawing looks'), which immediately distinguishes this from drawing_add/drawing_delete/freehand siblings. It also tells the agent where to get the id (chart_state). It doesn't explicitly name sibling alternatives, so not a 5.

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?

Provides concrete context: use distinct colours for measured vs projected levels and call chart_link after changes so the person can open it. It explains when to use it (after drawing exists) but doesn't mention alternatives or when not to use, hence 4.

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