gtm_builtin_variable

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

With no annotations, the description carries the full burden. It discloses that create enables and delete disables, which is helpful. However, it does not mention return values, permissions, idempotency, or side effects. This is minimal viable transparency but not particularly rich.

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 a single, front-loaded sentence that efficiently packs the resource, operations, and semantic nuances (enable/disable). No unnecessary words or redundancy.

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?

The tool has no output schema and no annotations, so the description should cover more. It covers the operations but omits return value expectations, list behavior, and any prerequisites or caveats. For a simple CRUD tool, this is adequate but not comprehensive.

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 all parameters have descriptions. The description itself adds little beyond the schema—it only restates that type is needed for create/delete, which is already captured. The baseline 3 applies because the schema does the heavy lifting.

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 the tool manages GTM built-in variables and enumerates the exact operations (list, create/enable, delete/disable). It explicitly mentions 'built-in variables', which distinguishes it from sibling gtm_variable. The verb 'manages' plus specific actions makes the purpose unambiguous.

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 implies usage for built-in variables only, but it does not explicitly name alternatives or provide when-to-use guidance. It does clarify that create means enable and delete means disable, which gives some context for action selection, but no explicit exclusions or comparisons to sibling tools.

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