app_get_var

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

The annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, indicating a safe, non-destructive, idempotent read. The description adds a useful behavioral cue with 'LIVE:', which implies the tool reads the current value at call time, possibly reflecting immediate state changes. This adds context beyond the annotations.

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 extremely concise at one sentence and front-loads the key information ('LIVE: read a global variable'). It is appropriately sized for a tool with a single parameter. However, it could have added a brief note on parameter usage without being verbose.

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?

The tool is simple (one parameter, no output schema, no nested objects), and the description combined with annotations covers the basic safety profile. However, it does not explain what the return value is or what 'LIVE' means in terms of consistency or caching. Without an output schema, the description should have clarified the return format, but the simplicity keeps it at a minimum viable level.

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 has only one parameter 'name' with no description, and the description does not explain what 'name' refers to (e.g., variable name format, case sensitivity, or how to find valid names). Since schema coverage is 0%, the description fails to compensate for this lack of detail, though the parameter name is self-explanatory to some degree.

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 states a specific verb ('read') and resource ('global variable from the app workspace'), making the purpose clear. It does not explicitly distinguish from siblings like app_set_var or app_get_code, but the verb 'read' and the resource 'variable' are unambiguous enough to differentiate it from most siblings.

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 a read operation and provides no explicit when-to-use guidance. It does not mention alternatives like app_get_code or app_sensor_snapshot, nor does it state when not to use it. The context is clear for a simple read, but the lack of any mention of when to prefer this over siblings leaves some ambiguity.

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