gtm_update_variable

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

The description discloses the fetch-merge-save pattern and safety constraint (sandbox only), adding value beyond the basic verb. No contradictions with annotations (none provided).

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?

Two concise sentences: first establishes purpose and scope, second adds behavioral detail and safety. No redundant information, every sentence serves a purpose.

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 description covers the operation, behavior, and safety constraints adequately for a simple tool with two parameters. However, it omits return value information, which would be useful given no output schema.

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?

While schema coverage is 100%, the description clarifies the merge behavior for updates_json, which is not fully captured by the schema alone. This adds meaningful context for parameter usage.

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 'Update' and resource 'variable', and specifies the scope 'sandbox workspace', distinguishing it from sibling tools that operate on other resources or workspaces.

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 updating variables in sandbox but does not explicitly state when to use this tool versus alternatives like gtm_create_variable or gtm_update_tag, nor provide when-not-to-use guidance.

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