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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so safety is covered. The description adds genuinely useful behavioral context beyond that: it discloses that only names come back and that values such as database URLs and credentials are never returned, which matters for an agent deciding whether this call can satisfy a data need.

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 waste; the core scope (names only) is front-loaded and the security-relevant caveat follows immediately.

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 no output schema, the description does the essential work of describing what is returned (names, not values), which is the key unknown for this tool. However, it says nothing about the required project/environment scoping or the other eight parameters, so it is only minimally complete for a 10-parameter tool.

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 0% across 10 parameters, so the schema provides no prose for any of them, and the description adds nothing about parameters either. The two required identifiers (projectId, environmentId) and the eight beon_* fields remain unexplained, leaving a significant compensation gap for a tool of this arity.

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 and resource ('List variable names only'), making the scope unambiguous and clearly distinguishing it from the sibling mutations railway_set_variable and railway_delete_variable. It does not, however, name any sibling or contrast itself with an alternative listing tool, so it stops short of full sibling differentiation.

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 explicit when-to-use statement or named alternative. The phrase 'values ... are never returned' implies the use case (safely discovering which variables exist without exposing secrets), but the agent must infer that. Adequate but with a clear gap.

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