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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds useful context that authentication is required and that the usage window is today. However, 'Requires your key' is ambiguous given the schema's deprecated optional vigil_key and preferred Bearer header, and no return or error behavior is disclosed.

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 no filler. The main result details are front-loaded, and the auth note is a single necessary additional sentence.

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 read-only tool with zero required parameters and no output schema, the description provides the high-level return contents and the auth expectation. It omits output shape and exact auth mechanism, but the schema covers the auth-header path, and the tool is simple enough that this is nearly complete.

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 the schema already documents the deprecated vigil_key parameter and the preferred auth-header behavior. The description adds no real parameter-level detail, and 'Requires your key' could even be misread as requiring the deprecated argument.

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 clearly identifies what the tool exposes: the current tier, its limits, and today's usage. It lacks an explicit verb like 'retrieves' and does not explicitly differentiate itself from siblings such as vigil_info or vigil_pricing, so it stops short of a top score.

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 usage context is implied: call this when you need your current tier, limits, or daily usage. However, there is no explicit when-to-use guidance, no mention of alternatives, and 'Requires your key' reads more as an auth prerequisite than as usage guidance.

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