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

Annotations already declare readOnlyHint=true, so the bar is lower, and the description adds genuinely useful context: only 'active' variables are returned, results come from the persistent V_t namespace, and X-License-Key authentication is required. The 'Read-only' sentence merely restates the annotation, but the auth and active-only scoping add real value.

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 compact sentences with the core scope front-loaded and no filler. The only slight redundancy is 'Read-only', which the annotation already conveys.

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?

An output schema exists so return values need not be explained, and both optional parameters plus the auth requirement are covered. What an agent needs to call this correctly is essentially present, with only the relationship to icx_var_get left implicit.

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 description coverage is 100%, so both parameters are already documented in the schema; baseline 3 applies. The description repeats that prefix matching is optional but adds no format or matching semantics beyond the schema's example values.

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 (lists) and resource (active variables and types) scoped to the persistent V_t swarm namespace. The 'all' scope implicitly separates it from the singular icx_var_get and the mutating icx_var_set, but no sibling is named explicitly.

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?

Usage is implied rather than stated: an agent can infer it should call this to discover keys before icx_var_get, and the description mentions optional prefix filtering. There is no explicit when/when-not guidance or named alternative among the many siblings.

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