variables_create

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

The description discloses the write nature and required configuration, but with no annotations, it fails to detail side effects, success/failure responses, or the effect on existing resources. It offers minimal behavioral context beyond the basic mutation fact.

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 extremely concise with a single sentence and a [WRITE] flag front-loaded. Every word is functional, but the brevity leaves out details that could be included without significant bloat.

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?

Given the tool's complexity (11 params, 6 required, nested objects), the description lacks guidance on constructing the request, valid parameter combinations, or expected outcomes. The absence of annotations and output schema further hampers completeness.

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 input schema has 11 parameters with only 18% description coverage, and the tool description adds no additional meaning for parameters like accountId, containerId, or the parameter array. The description does not compensate for the low schema coverage.

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 states 'Create a GTM variable' with a [WRITE] prefix, clearly indicating the verb and resource. It distinguishes from sibling tools like tags_create or triggers_create by specifying 'variable', but lacks additional context about variable types or the GTM service.

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 specifies prerequisites (GTM_MCP_ENABLE_WRITES=true and confirm=true), providing a when-to-use condition. However, it does not mention when not to use this tool or suggest alternatives, leaving the agent to infer usage scope.

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