List variables in a workspace

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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior. The description adds value beyond them by disclosing that only user-defined variables are returned, that built-ins are excluded, and that results include type and parameters. It also repeats the read-only nature, which is not a contradiction and reinforces safe usage.

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?

Three short sentences, each earning its place: the core purpose, the critical built-in vs user-defined distinction, and the targeting options. The main action is front-loaded with no filler or repetition.

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 a list tool, the safety profile is fully covered by annotations and the six-parameter schema is rich, including paging and default limit details. The description adds the main caveat (user-defined only) and expected response content. The only minor omission is not naming the exact collection/tool to use when built-in variables are needed, but this is not a blocking gap.

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 100%, and the schema already explains the path alternative, numeric containerId format, opaque pageToken, and limit default. The description's mention of 'path or accountId + containerId + workspaceId' only restates what the schema encodes without adding new parameter-level semantics. Baseline 3 applies.

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 opens with a specific verb and resource: 'Lists user-defined variables in a Tag Manager workspace with their type and parameters.' It also explicitly separates user-defined variables from built-in variables, preventing scope confusion and clearly distinguishing the tool from siblings like gtm_list_tags and gtm_list_triggers.

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 gives clear context: this tool returns only user-defined variables and notes that built-in variables are a separate collection, signaling when not to use it. It also states the two accepted ways to target a workspace—full path or the three IDs. It does not name a concrete sibling tool for built-ins, but the exclusion and targeting options are explicit enough.

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