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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint=false), so the bar is lower, and the description adds genuinely new behavioral facts not in the schema: it uses runtime calendar support, names the algorithm in every response, and discloses a $0.05 per-call cost paid over x402 (USDC on Base). That pricing constraint is decision-relevant for an agent. It stops short of explaining error behavior for invalid dates or out-of-range years.

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 sentence packing is dense but not padded — every clause (calendar list, Easter, runtime basis, algorithm naming, price) carries information. The price disclosure at the tail is slightly abrupt but not wasteful.

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 does some work in that direction by promising the algorithm name in every response, and it fully covers the operation space and all calendar targets. Annotations cover safety, so remaining gaps — exact response shape formalities and failure modes for bad dates or years outside 326-9999 — are minor for a read-only, idempotent converter.

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%, so 3 is the baseline, but the description adds real semantic mapping: 'Islamic (both the tabular civil calendar and the Umm al-Qura variant)' disambiguates islamic vs islamic-umalqura, and 'Easter Sunday ... in both the Gregorian and Julian reckonings' clarifies the rite western/eastern enum. This is meaning beyond the schema strings, so it earns above baseline.

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?

Specific verb (convert) plus resource (Gregorian date → other calendar systems), with the supported calendar systems enumerated concretely and an additional distinct operation (Easter computation) called out. An agent can separate this from siblings like timezone_convert or base_convert purely from the text, since the calendrical conversions named (Islamic, Hebrew, Japanese era, ROC, Buddhist, Persian) are unique to this tool.

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?

The description implies usage via its two operations — convert a date, or compute Easter for a year — but never states when to prefer this tool over siblings (e.g., timezone_convert) or any exclusions/preconditions. The routing between convert and easter is really left to the schema's op enum rather than explained as guidance in the prose.

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