add_variable

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

With no annotations, the description carries full burden. It discloses type-dependent behavior, variable naming hint ($ prefix), and return type. However, it omits side effects (e.g., whether variable must exist), error conditions, and permission requirements.

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 highly concise: a one-line operation summary, behavioral rule, then clear Args section. Every sentence adds value with no 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?

For a simple 2-param tool, the description covers purpose, parameter semantics, and return type. It lacks context on variable existence, creation, or global vs user scope, but overall is sufficiently 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?

Schema coverage is 0%, so the description must fully compensate. It provides clear semantics: var_name should start with $, value is either numeric (added) or text (appended). This adds significant value beyond the raw schema types.

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 operation 'Add to / extend a global show variable' and specifies type-dependent behavior (sum numeric, concatenate text). The verb 'add' distinguishes it from sibling tools like set_variable (overwrite) and add_user_variable (user-level).

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 explicit guidance on when to use this tool versus alternatives like add_user_variable or set_variable. The name implies addition, but the description does not clarify scope or prerequisites, leaving inference up to the agent.

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