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

Annotations already declare readOnlyHint and destructiveHint=false, so safety is covered. The description adds genuinely useful operational context beyond that: business rules (no Shabbat or Jewish festival days), operating hours (11:00-19:00 Israel time), and surcharge behavior on certain days. What the returned price/dates represent is disclosed.

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?

One dense but well-structured sentence, front-loaded with the resource ('Where and when we deliver') followed by the returned fields and rules. No filler or redundancy, though the run-on structure could be slightly cleaner.

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?

For a read-only lookup with no output schema and only two optional params, the description adequately enumerates the returned content and the governing rules. The only minor gap is whether omitting date returns the full schedule, but overall it is complete enough to invoke 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?

The city enum is self-documenting with 16 values, and the date param has a schema description plus a format pattern. The description adds invocation semantics for date ('check that day'), clarifying its purpose beyond the bare schema note. Limited remaining gap makes this better than 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?

States a specific resource and enumerates what it returns (cities, price, next delivery dates with surcharge, delivery rules). An agent clearly understands this is a delivery-availability lookup. It doesn't explicitly contrast with siblings like quote or create_order, but the purpose is unmistakable.

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?

'Pass a date to check that day' gives concrete invocation guidance for the optional date parameter, and the overall context implies pre-order use. However, it never states when to prefer this over quote or create_order, nor what happens when no date is passed (all dates returned?). Usage is implied rather than explicit.

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