Draw.io MCP Server

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

With no annotations provided, the description carries full burden. It discloses the partial update behavior ('Only provided fields are modified'), which is valuable. However, it doesn't mention permission requirements, error conditions (e.g., invalid cell_id), mutation effects, or response format. For a mutation tool with zero annotation coverage, this leaves significant behavioral gaps.

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 concise sentences with zero waste. First sentence states core purpose, second adds crucial behavioral detail about partial updates. Perfectly front-loaded and efficient.

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 5 parameters, 100% schema coverage, but no annotations and no output schema, the description is minimally adequate. It covers the partial update behavior but lacks information about permissions, error handling, and return values. The schema handles parameters well, but behavioral context is incomplete.

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 100%, so the schema already documents all 5 parameters thoroughly. The description adds no additional parameter semantics beyond what's in the schema. Baseline 3 is appropriate when schema does the heavy lifting.

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 clearly states the specific action ('Update properties'), target resource ('existing edge'), and identifier mechanism ('by its ID'). It distinguishes from siblings like 'add-edge' (creation) and 'edit-cell' (different resource type).

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 usage when modifying an existing edge, but doesn't explicitly state when to use this vs alternatives like 'set-cell-data' or 'edit-cell'. It mentions partial updates ('Only provided fields are modified'), which provides some contextual guidance but lacks explicit exclusions or prerequisites.

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