gtm_update_variable

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

With no annotations provided, the description carries the full burden. It discloses an important behavioral requirement: the need to provide a full resource, implying a complete replacement. However, it does not mention permissions, reversibility, or failure modes, leaving significant gaps for a mutation tool.

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?

A single sentence with no redundant words, front-loaded with the action verb. It is concise and structured effectively.

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 tool has 5 required parameters, no annotations, and no output schema. The description provides only a minimal explanation of its purpose and the key payload requirement. It does not cover how to obtain IDs, the result or response, error cases, or the fact that this is a full replacement operation. Given the complexity, the description is insufficient.

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%. The description only hints that variable_json must be a full GTM Variable resource, but does not explain the purpose of the four ID parameters or how to construct the JSON. The parameter names are self-explanatory, but the description does not compensate for the lack of schema descriptions.

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 a specific action ('Update') with a clear resource ('existing variable') and specifies the required payload type ('full GTM Variable resource (JSON string)'). This clearly distinguishes it from sibling tools like gtm_create_variable and gtm_delete_variable.

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 the tool is for modifying an existing variable, but it does not explicitly state when to use it versus alternatives, nor does it mention prerequisites or exclusions. There is no reference to sibling tools or 'when not to use' guidance.

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