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

Annotations already provide readOnlyHint=true and openWorldHint=false, and the 'say whether' language is consistent with those. The description adds real behavioral value beyond the annotations by disclosing the roll-forward mechanism and the governing statute (CCP §12a), which the agent would otherwise not know.

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 sentences with zero waste. The core behavior is front-loaded in the first sentence, and the second sentence provides actionable usage guidance that earns its place.

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 single-parameter, read-only tool with no output schema, the description fully explains what the caller receives: a court-day determination plus the next roll-forward date under §12a. Nothing an agent needs in order to call it correctly is missing.

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 coverage is 100%, so the schema already documents the date parameter with its format and 'The date to check.' The description adds mild context by implying the date is a filing or deadline date, but it adds no substantive semantics beyond what the schema already provides, so the baseline of 3 applies.

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 precise action — determining whether a given date is a California court day and, if not, rolling forward to the next one under Code of Civil Procedure section 12a. This distinguishes it clearly from siblings like california_court_holidays (a static holiday list) and california_add_court_days (which adds days to a date) without needing to open their schemas.

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 second sentence gives explicit when-to-use guidance: 'Use this before asserting that a filing date or a deadline falls on a working day.' It names the decision context precisely, though it does not mention exclusions or route the agent to alternative sibling tools for other scenarios.

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