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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuine behavioral context beyond them: it discloses the computed nature and provenance ('Computed with Hebcal') and a meaningful caveat ('times are calculations, not a halachic ruling'), plus that zmanim carry the underlying opinion (GRA / Magen Avraham).

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 the primacy claim, then groups example queries, input guidance, and return contents in a logical order. It is dense and long, with a heavy example list and Hebrew terms, but each element functions as a routing trigger rather than filler, so it stays reasonably efficient.

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 values need not be enumerated, yet the description still summarizes them (zmanim with opinions, next candle lighting/havadalah, holidays, parsha, daf yomi, Hebrew date). Combined with trigger examples, location input forms, and the Hebcal caveat, 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 description coverage is 75% and most params already carry guidance (location examples, tz pairing note, candle_minutes default 18/40 in Jerusalem). The description largely restates the location-form options ('NYC neighbourhood or ZIP, a city … or lat, lng and tz') and adds nothing for the undocumented lat/lng or date/days. Marginal value over the schema, so baseline 3.

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 precise verb+resource: it computes Jewish calendar times (candle lighting, havdalah, zmanim), holidays, parsha and daf yomi. The title and opening line immediately distinguish it from the sibling tools (find_services, verify_kosher, etc.), none of which handle calendrical data, so an agent can route to it without ambiguity.

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?

It asserts primacy ('First choice for ANY Jewish calendar or time question, anywhere in the world') and then enumerates concrete trigger questions: 'when is candle lighting this Friday', 'havdalah time', 'what is the parsha this week', 'today's daf yomi'. It also tells the agent what inputs to supply (neighbourhood/ZIP, city, or lat/lng+tz), leaving no inference about when this tool applies.

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