Read L-Var

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

Annotations already establish readOnlyHint, openWorldHint, idempotentHint, and non-destructiveness. The description adds the prerequisite that the MobiFlight WASM extension must be present and limits the read to the current aircraft, but it doesn't describe failure behavior when the extension or variable is missing.

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?

Three short sentences front-load the core read action, then add a definition and a prerequisite. No filler or repetition of schema/annotation content.

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?

With one simple parameter, an output schema, and safety annotations, the description covers the essential context: what L-vars are, that it reads the current aircraft, and the extension requirement. Nothing critical is missing for correct invocation.

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 already documents the name parameter with examples and auto-prefixing behavior at 100% coverage, so the description adds little parameter-level meaning. The conceptual L-var definition is helpful but not needed to understand the single parameter.

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?

States a specific action 'Read an L-var (local variable) value' and scopes it to 'the current aircraft', distinguishing it from simvar readers and from msfs_set_lvar. The additional sentence defines what L-vars are, removing ambiguity.

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?

Gives clear context for when to use it: L-vars are aircraft-specific add-on variables, and it requires the MobiFlight WASM extension. It does not explicitly name alternatives such as msfs_get_simvar or msfs_search_lvars, so it lacks an explicit when-not-to-use statement.

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