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

Annotations already cover read-only, idempotent, closed-world behavior, so the description is free to add the things annotations cannot: that Day 90 and Easter Sunday are computed 'by our count', that days-until is measured in US Eastern time, and that no app store links exist yet. That last point is a real hallucination guard, preventing the agent from fabricating store URLs.

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 when-to-call clause is front-loaded and every clause carries information. However, the return inventory is delivered as one long run-on sentence, and the trailing example largely restates the triggers already listed, so it is slightly denser and more redundant than ideal.

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 zero parameters, an output schema, and full annotation coverage, the description needs only to say when to call and what comes back, and it does both plus the caveats about app availability and date computation. Nothing an agent needs in order to invoke 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the 4 baseline applies. No parameter guidance is missing because no inputs exist.

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 names exactly what the tool returns: the official 2027 start date plus its source page, Day 90 and Easter Sunday by the program's count, days until Day 1 in US Eastern time, follow channels (web live, iOS/Android coming soon), and the signup link. That is concrete enough to separate it from get_day (a specific day's content) and get_program_info (general program material). The name is vague on its own, but the description removes all ambiguity.

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?

It gives explicit call triggers: user asks when the 90 days start, how long until Day 1, or whether an app exists, reinforced with a sample query. There are no when-not conditions and no named alternatives (e.g. it never says to use get_program_info instead for broader program questions), so it falls short of a 5.

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