Set Variable

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

Annotations already provide idempotentHint=true, readOnlyHint=false, and destructiveHint=false, and the description adds session-scoping context ('in the session') and the notion of later reuse. However, it does not disclose behavior around overwriting existing variables, omitting the value, or whether a session must exist, so some gaps remain.

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 two short sentences with no filler. The core action is front-loaded in the first sentence, and the second sentence provides a concrete use case. Every word earns its place.

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 setter, the description is adequate, but it lacks important invocation context: it does not mention that a session must exist, what happens if value is omitted, or how session_id relates to the 'session' mentioned. With no output schema and sibling tools, a bit more guidance would make it fully 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 100%, meaning all parameters (name, value, session_id) have descriptions. The tool description adds little beyond restating 'variable' and 'session', so it meets the baseline 3 for high schema coverage but provides no extra semantic detail.

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 uses a specific verb ('Store') with a clear resource ('a variable in the session'), and the scope ('for later use') distinguishes it from sibling tools like rlm_get_variable, which retrieves variables, and rlm_load_context, which loads context. It directly states what the tool does and is 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 explicitly instructs when to use the tool: 'Use this to save intermediate results during RLM processing.' This gives clear context, though it does not mention alternatives or when not to use it, so it falls short of a 5.

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