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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered. The description adds genuinely non-obvious context: the conversion uses Saudi Arabia's official Umm al-Qura calendar (Hijri dates vary by convention, so this matters) and that results include the weekday and Eid dates. It does not disclose output shape or edge cases beyond that.

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 compact sentences plus an attribution URL; nothing is padded. The leading worked example ('1 Ramadan 1448 AH is Monday, 8 February 2027') usefully previews the output format including the weekday, though it is not labeled as an example and slightly precedes the actual statement of purpose.

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 carries the burden of saying what comes back — it does so briefly (converted date, weekday, Eid dates). With five all-optional, fully documented parameters and complete annotation coverage, only the direction-selection mechanics remain underspecified.

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 baseline is 3. The description implies bidirectional conversion via 'Hijri ↔ Gregorian', which helps interpret the terse 'mode' enum labels (g2h/h2g, schema-described only as 'Convert'), but it adds no guidance on which parameter set to populate for each direction.

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 names a specific verb and resource ('Convert dates Hijri ↔ Gregorian') and scopes it to the Umm al-Qura calendar, which no sibling tool covers. It stops short of explicitly distinguishing itself from nearest neighbors like date_calculator or ramadan_countdown_calculator, but the resource is unambiguous.

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?

Usage is implied by the stated scope: this is the tool for Hijri↔Gregorian conversion. There is no explicit when-to-use/when-not guidance and no mention of the adjacent siblings (date_calculator, day_of_week_calculator, ramadan_countdown_calculator) that could plausibly be confused with it.

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