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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and closed-world, so the safety profile is fully covered. The description adds the useful 'enabled only' scoping semantics, but says nothing about result ordering, pagination, or size limits for a list operation. With annotations carrying the safety burden, this is adequate but thin.

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 first sentence is front-loaded and efficient. The trailing 'Tools revision: 5c9bea8f.' line adds no information an agent can use for tool selection or invocation, so it dilutes rather than earns its space.

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?

An output schema exists, so return values need no explanation, and annotations cover the safety profile. The remaining gap is the workspace identifier format and how to obtain one (presumably via gtm_list_workspaces), which the description does not address.

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% for the single required 'workspace' parameter, and the description says nothing about its expected form (numeric ID, resource path, or name). Since this is a 1-param tool with zero documentation anywhere, the description needed to compensate and does not.

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?

States a specific verb ('List') and a specific resource ('enabled built-in variables') scoped to a workspace, which is clear enough to act on. It does not, however, explicitly distinguish itself from siblings like gtm_list_variables (user-defined) or gtm_enable_built_in_variable, leaving the agent to infer the built-in vs. custom split.

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?

There is no statement of when to use this instead of gtm_list_variables or gtm_enable_built_in_variable, and no prerequisite information such as needing an existing workspace. At best the word 'enabled' implies it filters out disabled variables, but that is never stated as usage guidance.

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