List Tag Manager variables

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

Annotations already declare read-only behavior. The description adds transparency about data sources (live container vs workspace enabled-built-ins) and the consequence of missing built-in variables, which complements the annotation without contradiction.

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 description is compact and well-structured, efficiently conveying the distinction between custom and built-in variables and their relevance without unnecessary verbosity. The paragraph separation aids readability.

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?

Given the presence of an output schema, the description does not need to detail return format. It adequately covers the core purpose and provides contextual nuance about variable sourcing and trigger dependencies, making it sufficiently complete for an agent to use correctly.

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% and the description does not explain the parameters (gtm_account_id, gtm_container_id). Although names are self-explanatory, the description fails to compensate for the lack of schema-level documentation, leaving their role and default behavior ambiguous.

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 clearly states it lists GTM variables, distinguishing custom (from live container) and built-in (from workspace enabled-built-ins), and explains the practical significance (trigger references). This is specific and differentiates from sibling tools that handle other GTM resources.

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 provides meaningful context about when variables matter and how they are sourced, implicitly indicating this tool is for checking variable availability. It does not explicitly compare with alternatives, but the purpose is clear enough for an agent to select it for variable-related queries.

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