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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is low. The description adds one genuinely useful trait — returned content has links pointing at this server — but says nothing about size, truncation, or what the reference files contain.

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, front-loaded with what is returned and followed by the audience condition. No filler, though the phrasing is slightly elliptical ("The daycal skill's SKILL.md...").

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 a single optional enum parameter, an explicit audience, and no output schema required, the description covers enough for an agent to call it correctly. The one gap is that it never enumerates what the five reference files are for, leaving the enum names to speak for themselves.

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% and the single enum parameter is fully documented in the schema, so baseline 3 applies. The phrase "or one of its reference files" gestures at the parameter but adds no semantics beyond the enum already in the schema.

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 the concrete resource returned — the daycal SKILL.md or one of its named reference files — which separates it from siblings like get_types, get_calendar_refs, or explain. It is clear but relies on the title for the explicit verb and doesn't fully differentiate the reference-file variant from other doc-style tools.

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?

"For agents that cannot install skills" gives a clear audience/condition for when this tool is the right choice. It stops short of naming an alternative for agents that *can* install skills, so the routing guidance is one-sided.

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