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

Goes well beyond the readOnly/idempotent annotations: discloses the 1 MB input cap, the 2,000-event cap with a `truncated` marker, that only VEVENT is returned (to-dos/journals/alarms skipped), that unknown TZIDs stay floating with a per-event warning, that all-day `end` is inclusive, that non-VCALENDAR input yields an uncharged 422, typical latency, price, and the untrusted-data warning. This is the exact behavioral context annotations cannot carry.

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?

Front-loads purpose and the sibling disambiguation, then layers constraints, error behavior, and economics in short clauses. Dense but nearly every sentence carries actionable fact; the price/free-tier/docs sentences edge toward boilerplate but are genuinely decision-relevant for a paid x402 endpoint.

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?

An output schema exists, so return shape need not be restated, and the description fills every remaining gap an agent needs: input envelope, truncation behavior, filtering of non-VEVENT components, timezone edge cases, error semantics, and cost. Nothing needed to call 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?

Schema description coverage is 100%, so the schema already documents `ics`, `timezone`, and `max_events`. The description mostly restates those semantics ('optional `timezone` for floating times and `max_events`'), adding only the unknown-TZID fallback rule, which is worth having but does not exceed the baseline for fully documented schemas.

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 resource ('Parse an iCalendar file into JSON events') and immediately distinguishes itself from the sibling it is not: 'To write one use build_ics_event.' An agent can route between the two calendar tools without opening either schema.

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?

Explicitly names the alternative tool (build_ics_event) for the write direction, and the pricing/free-tier lines imply the conditions of use. It stops short of stating when this tool is the right choice versus e.g. expand_rrule or convert_time, so it is clear context rather than full when/when-not guidance.

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