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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds useful semantics — persistence across runs and per-scope values — but says nothing about pagination, volume, or what a returned entry contains.

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?

Two short sentences with zero filler; the operation and its scope are front-loaded. The second sentence earns its place by clarifying what 'scoped' variables mean in the returned data.

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 parameter and no output schema, the description should sketch what a listed variable looks like (name, value, scope) since the agent cannot inspect a return schema. Persistence semantics are covered, but the response shape remains unspecified.

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% and the single required app_id is documented with a pointer to list_apps, so the schema does the heavy lifting. The description only echoes that variables belong to an app, adding no format or sourcing 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?

States a specific verb and resource ("Lists the stored variables of an app") and adds a definition of what a variable is, which is more than a restatement of the name. It does not distinguish itself from siblings like create_variable or list_apps, so an agent must infer the read-only enumeration role.

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?

There is no statement of when to call this versus alternatives (e.g. create_variable to add one, or where to find app_id beyond the schema). The 'keep values between runs' note is conceptual background, not usage guidance.

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