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

Annotations already declare this is a non-read-only, non-destructive, closed-world operation. The description adds useful behavioral context by explaining that the variable keeps a value between runs, but it omits duplicate-name behavior, required permissions, and what the creation returns.

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 definition is a single front-loaded sentence with no wasted wording. It conveys the action, persistence semantics, and target context efficiently.

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 simple three-parameter create tool with annotations and partial schema descriptions, the description covers the essential purpose and persistence behavior. It still leaves gaps around return behavior, duplicate handling, and relationship to list_variables, so it is adequate rather than complete.

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?

The schema documents app_id and scoped, covering two of the three required parameters, while name is self-evident. The description does not add parameter-level meaning, but with 67% schema coverage the schema already carries most of the burden.

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 gives a specific verb and resource ('Creates a stored variable') and explains the core concept of persistence between runs. It does not explicitly distinguish this from the sibling list_variables tool, but the create action is clear.

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?

It states the usage context ('for blocks with a variable_id setting'), which implies when the tool is relevant. However, it does not mention alternatives such as list_variables for inspecting existing variables, nor does it give any 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.