gtm_update_variable

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

With no annotations provided, the description carries the full burden of behavioral disclosure, but it only states that the tool updates a variable. It does not mention optimistic locking via the fingerprint, potential side effects on workspace versioning, whether the update is partial or full replacement, or auth/rate-limit considerations.

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 concise sentence with no redundant wording or filler. It front-loads the core action and resource, making it easy for an agent to scan.

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 mutation tool with six required parameters, a nested variable object, no output schema, and no annotations, this one-sentence description is insufficient. It does not explain the optimistic-locking fingerprint requirement, what the variable object should contain, or what the update implies for the workspace.

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 high at 83%, so the schema itself adequately documents most parameters. The description adds no extra meaning about the 'variable' object or how the fingerprint/prameters interact, but with this level of schema coverage, a baseline of 3 is appropriate.

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 verb 'Updates' and the resource 'an existing variable in GTM', which distinguishes it at a basic level from create, delete, list, and get variable tools. However, it does not explicitly distinguish it from other update tools like gtm_update_tag or gtm_update_trigger, relying mostly on the tool name for precision.

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?

No guidance is given on when to use this tool instead of alternatives such as gtm_create_variable, gtm_get_variable, or gtm_delete_variable. An agent is left to infer usage from the verb 'Updates' alone, with no mention of prerequisites like fetching the variable or its fingerprint first.

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