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

No annotations are provided, so the description carries the full burden, and it discloses nothing: not whether 'prev month' is computed from today or from the supplied date, not the return shape, not whether the result is a name, number, or date range.

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?

Extremely short, but this is under-specification rather than conciseness. The single duplicated phrase occupies the space that a real explanation should fill, so nothing is front-loaded because nothing is said.

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 one-parameter date tool with no annotations and no output schema, the description should clarify the default for the optional 'date' and what is returned. Neither is addressed, leaving the calling agent to guess.

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?

With a single parameter and 100% schema description coverage, the schema already documents the 'date' field, so the baseline of 3 applies. The description adds no clarification about the optional date's default or its role in the computation.

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 'Prev Month: Prev Month' merely restates the tool name with no added meaning. An agent can infer it returns the previous month, and the sibling set (x402-next-month, x402-month-start, x402-month-end) narrows the intent, but no verb, output, or scope is actually stated.

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?

No guidance whatsoever on when to use this versus x402-next-month, x402-month-start, x402-month-name, or other date siblings. No prerequisites, no exclusions, no context.

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