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

Annotations already establish read-only, idempotent, non-destructive, closed-world behavior. The description adds real context beyond that: that it is a bootstrap call, that it returns a pointer to the signing secret via get_webhook_secret, and that supplying the installed skill version triggers an outdated check. No auth/rate-limit details, but the added behavioral value is genuine.

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 imperative opener is correctly front-loaded. However, the middle clause describing Daycal's product ("a page where people book time with them that matches their real week (trips, holidays, cutoffs, focus blocks, limits, several calendars)") is marketing framing that does not help an agent select or invoke the tool, and it bloats an otherwise dense paragraph.

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 no output schema, the description must describe the return payload, and it does so thoroughly by enumerating each artifact. That is the key completeness requirement here. It is slightly less complete about ordering/dependency with the sibling skill tools, but nothing essential is missing for calling it.

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% and the single parameter is optional, so the schema already carries the baseline. The description nonetheless adds effect semantics the schema does not state — that passing the version causes the server to tell you whether it is outdated — which is exactly the kind of meaning a schema cannot convey.

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?

States a specific verb and enumerates the concrete artifacts returned (daycal.d.ts, stdlib reference with examples, starter rules.js, skill version, signing-secret pointer, plans/prices). The purpose is legible, but bundling types + reference + version check + pricing into one call muddies the single-resource framing, and no sibling (e.g. get_skill) is named to differentiate.

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?

"Call this first, every session" is explicit and unambiguous about timing, which is rare and valuable. It stops short of the 5 bar because it never names an alternative or a when-not condition relative to siblings like get_skill or get_calendar_refs.

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