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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description contributes one real behavioral detail – that only *enabled* built-in variables are returned – but says nothing about how to see disabled ones, ordering, or whether the result is workspace-scoped versus container-scoped.

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 core sentence is front-loaded and wastes nothing. The trailing 'Tools revision: d80f65c0.' is build metadata rather than information an agent needs to select or invoke the tool, so it is minor filler.

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 not be described, and annotations cover the safety semantics. However, for a tool whose only parameter is 0%-documented, the description should explain how to address a workspace and note that this pairs with gtm_enable_built_in_variable; those gaps keep it at merely adequate.

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 only repeats the word 'workspace' without explaining the expected identifier format (workspace ID, path like accounts/x/containers/y/workspaces/z, or name). It adds essentially no meaning beyond the bare schema.

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 and resource ('List the enabled built-in variables') scoped to 'a workspace', which is clear enough to distinguish it from gtm_list_variables (user-defined variables) and gtm_enable_built_in_variable. It does not explicitly name those siblings, so the differentiation is inferable rather than stated.

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?

Usage is only implied: the reader can guess this is a read step taken before or after enabling built-ins, but the description never says when to call it versus gtm_list_variables or gtm_enable_built_in_variable. No prerequisites (e.g. needing an account/container/workspace path) are mentioned.

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