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

With no annotations, the description carries the full behavioral burden. It discloses a critical privacy trait: 'never the values,' and adds that actual values are 'substituted at tool-call execution time.' This goes beyond the basic list semantics and helps an agent understand what the tool will and will not expose.

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 compact and front-loaded: the first sentence states the core purpose, the second specifies return contents and the key privacy guarantee, and the third provides practical usage timing. Every sentence contributes value without redundancy.

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?

For a zero-parameter list tool, the description is complete. It explains what is returned (names + timestamps), what is not returned (values), when to use it, and the execution-time substitution behavior. An agent has enough context to decide when to call it and what to expect.

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 tool has zero parameters, so there is no parameter ambiguity. The description adds context around the kinds of stored values it refers to by giving examples like 'alice-test-account' and 'staging-url,' which helps the agent understand the domain without needing parameter documentation.

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 action and resource: 'List the names of secret variables the user has stored for this account.' It also clarifies what is returned ('NAMES + updated timestamps') and explicitly distinguishes itself by noting 'never the values.' This is a precise, unambiguous purpose.

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 gives explicit when-to-use guidance: 'Use this BEFORE asking the user for any URL, credential, or API key to see if a relevant one is already saved.' It does not identify alternatives or when not to use it, but the context is clear and actionable.

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