set_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. It indicates the tool stores values but does not specify whether it overwrites existing variables, the scope (session vs. persistent), or any size limits. This is adequate for a simple store but lacks thoroughness.

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 of 15 words with no unnecessary detail. Every word contributes to understanding the tool's function and usage, making it highly efficient.

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 two-parameter tool with no output schema, the description covers the essential purpose and usage. It does not detail variable naming conventions or persistence, but these are minor omissions given the tool's simplicity.

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 input schema provides basic descriptions ('Variable name' and 'Variable value'), and the tool description adds context by explaining how these parameters are used in requests. This goes beyond the schema alone, earning a score above baseline.

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 that the tool stores values (like auth tokens) for reuse in requests via template syntax. It distinguishes itself from siblings like get_variables (which retrieves) and execute_request (which executes), making its 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 when storing values for later request reuse via {{varname}} syntax. However, it does not explicitly state when not to use it or mention alternatives like direct parameter passing, leaving some room for interpretation.

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