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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive, so the safety profile is covered. The description adds real behavioral value by disclosing both return artifacts (Mermaid source and SVG) and the steps-mode line syntax, going beyond the structured fields.

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 front-loaded sentences that state the core transform first, then the steps-mode syntax detail. Little waste, though the syntax example could be slightly tighter.

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?

A read-only transformation tool with no output schema, so the description is right to name the outputs. It covers mode/input adequately but omits the direction parameter, leaving a small gap for a three-parameter tool.

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 clarifies the three mode inputs and gives concrete steps-mode syntax with branch examples, but says nothing about the direction parameter (vertical/horizontal), leaving one of three 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?

States a specific verb (turn ... into) with the exact input types and the concrete output (Mermaid source and SVG diagram). No sibling tool produces flowcharts, and the description makes the resource 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?

The description implies three input sources via the mode names but never states when to choose code vs steps vs mermaid, nor any exclusions or prerequisites. Usage is inferable but not explicitly guided.

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