Delivery date and fee

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely non-obvious behavioral context beyond that: fees are in Toman with 0 = free, null means the item never ships free (bulky goods), same_day_seconds_left > 0 signals same-day delivery is still possible, and estimates assume a default Tehran address.

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?

The primary purpose and the usage trigger are front-loaded, followed by compact field-semantics notes. Every sentence carries information an agent needs (units, free-shipping condition, null meaning, same-day flag) with no filler.

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 an output schema present, the description need not describe the return shape, and it correctly focuses on interpreting the returned values. Combined with rich annotations and a fully documented single parameter, nothing an agent needs to call this tool 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?

There is a single parameter and schema coverage is 100%; the schema already documents product_id, including where to obtain it ('from mk_search / mk_browse'). The description only reinforces the per-product scope and adds no syntax or format detail beyond the schema, so the baseline 3 applies.

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 states a specific verb and resource ('Get the nearest delivery slot and shipping fee for one product') and immediately scopes the geography ('Tehran courier and post to other cities'). No sibling tool (mk_search, mk_deals, mk_product, etc.) covers shipping, so the agent can route to this tool unambiguously.

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 gives a concrete trigger phrase — 'Use for "when will it arrive / how much is shipping"' — and implies the per-product scope ('for one product'). It does not name an alternative or exclusion (e.g. how to get basket-level shipping for many items), so it stops short of explicit when-not guidance.

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