Create a Google Tag Manager variable by specifying account, container, workspace, and the variable object.
Create a GTM variable (full variable object).
| Name | Required | Description | Default |
|---|---|---|---|
| variable | Yes | ||
| account_id | Yes | ||
| container_id | Yes | ||
| workspace_id | Yes | ||
| connection_id | No | ||
| session_token | No |
Changes observed during successful MCP inspections.
v0.1.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden of explaining behavior. It only implies write/mutation via 'Create' and offers no information about authentication, permissions, side effects, validation, duplicate handling, or response behavior.
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 concise and free of filler, but it is under-specified for a tool with six parameters and a nested object. There is no structural break or additional detail that would make the short length feel sufficient.
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 tells the agent what action to take but not enough to invoke the tool correctly. Given no output schema, no annotations, a nested variable object, and zero schema description coverage, the single-sentence description leaves critical details about variable structure and required IDs unresolved.
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%, and the description adds essentially no parameter-level meaning. The 'variable' parameter is implied but not explained; account_id, container_id, workspace_id, connection_id, and session_token are all left undefined, with no guidance on their roles or formats.
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 uses a specific verb ('Create') and names the resource ('GTM variable'), making the core operation clear. The parenthetical '(full variable object)' adds a small hint about the expected payload shape, though it does not explicitly differentiate this from gtm_update_variable or other create tools.
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?
No guidance is provided about when to use this tool versus gtm_update_variable, gtm_list_variables, or the tag/trigger create tools. There is no mention of prerequisites, required context, or conditions that would steer an agent toward this tool.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.