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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and openWorld=false, so safety is covered structurally. The description adds real behavioral value beyond them: 'Needs no API key' (auth requirement) and the fact that version_only returns a bare version string sufficient for cache validation.

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?

Three tight sentences, front-loaded with what the tool returns, then when to use it, then the special-mode caveat. No filler or restatement of the name.

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-optional-parameter documentation fetch with no output schema, the description fully covers return content (full markdown vs version string), auth, and motivation. An agent has everything needed to call it correctly.

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 boolean's meaning is already documented in the schema, so baseline is 3. The description adds purpose-level meaning by explaining that the version string 'is enough to tell whether a cached copy is current' – a rationale the schema text does not supply.

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?

Names a specific resource (the relay's SKILL.md guide) and enumerates its coverage: events vs records, schema grammars, the poll loop. No sibling tool in the list does anything similar, so an agent can immediately separate it from the row/agent/app 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?

Gives two concrete usage contexts (understanding how other tools fit together, refreshing a cached copy) and a third narrow one via version_only for cache-currency checks. Clear context, though it states no when-not-to-use or explicit alternative.

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