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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds real behavioral context beyond that by stating the creation happens in the workspace DRAFT, warning the agent the change is staged rather than live. It does not cover naming-collision behavior, required container/workspace resolution, or permissions.

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 front-loaded sentence with the scope ('workspace DRAFT') before the type list, and zero filler. Every clause contributes either the resource, the scope, or the supported variants.

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 an 8-parameter mutation tool with no output schema, the description is adequate but thin: it never says what the call returns (e.g., a created variable ID or name) that the agent would need to reference the variable later, nor does it mention the container/workspace resolution rules or that a publish step follows. Annotations and schema cover the rest, so the gap is real but not severe.

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 coverage is 75% and the property descriptions already explain the per-type meaning of key and value, container disambiguation and workspace defaulting. The description's list of variable kinds only restates the type enum, adding no new parameter semantics, so the documented schema carries the load.

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 gives a specific verb ('Create') and resource ('variable') plus a scope ('workspace DRAFT') and enumerates the five supported variable kinds, which maps exactly onto the type enum. An agent can tell it apart from gtm_create_tag and gtm_create_trigger because the resource differs, though the description never names those siblings to make the distinction explicit.

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 phrase 'in the workspace DRAFT' implicitly tells the agent this is a staged change that is not live until published, but there is no explicit when-to-use or when-not-to-use guidance and no pointer to gtm_publish or gtm_create_tag as the follow-up/alternative. Usage is inferable rather than stated.

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