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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered; the description adds real behavior beyond that — the previewId is valid 30 minutes and bound to exactly this source, and dependent tools refuse without it. It also discloses that a failed run returns the error instead of slots. Only the absence of any note on compute cost or live-event side effects keeps it from a 5.

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?

Purpose is front-loaded in the first clause, and the return shape, lifecycle, and workflow advice follow in a compact paragraph with no filler. It is dense and slightly run-on, which costs it the top score, but every sentence carries information.

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?

There is no output schema, so the description must carry return semantics — and it does: ok/error behavior, warnings, slotCount, byDay with a date/slot-time example, and diff against the live version. Combined with the previewId lifecycle and the workflow instruction, an agent has everything needed to call and interpret 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 description coverage is 100%, so the schema already documents all four parameters including the rules_js/version_id 'omit to preview a stored version' relationship and event_type slugs. The description restates the rules.js-or-stored-version choice but adds no format or syntax detail beyond the schema. Baseline 3 applies when the schema does the heavy lifting.

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+resource ('validate rules.js ... and run it against the owner's live events') and frames the outcome ('Show what the owner's page would offer'). No sibling tool does previewing, so it is trivially distinguishable from list_versions, explain, and get_skill.

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 explicit operational guidance ('Run after every change and show the owner a few days of slots') and states a gating condition: push_config, or activate_version on a draft, refuses without the previewId. It stops short of naming alternative tools or an explicit when-not-to-use case, so it is a strong 4 rather than a 5.

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