USPS Holiday Shipping Deadlines MCP

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 real value beyond that by disclosing the response shape (per-service send-by date, days left, on-time flag) and the derived 'slowest cheapest service still on time' output, which annotations cannot convey.

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 purpose and output are front-loaded in the first clause, with destination formats following as supporting detail. It is a single dense sentence that stays on topic, though the long enumeration of destination examples makes it slightly heavy.

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 carries the burden of explaining return values and does so adequately (per-service send-by dates, days left, on-time status, recommended slowest-cheapest option). Combined with full schema coverage and rich annotations, an agent has enough to call and interpret 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 coverage is 100%, so the baseline is 3, but the description goes further by enumerating the accepted destination forms (lower48, state/territory, country, USPS region, APO/FPO/DPO ZIP with an example) that the schema only vaguely calls 'Where the package goes'. It also restates the ship_date default, which is already in the schema, so it is not a full 5.

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 opens with a specific verb and resource ('For a ship date ... and a destination, lists each USPS service with its send-by date, days left and whether it is still on time'), so an agent knows exactly what it returns. It does not name the sibling tools (get_usps_holiday_shipping_deadlines, get_military_mail_deadline) to differentiate itself, which keeps it from a 5.

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 context is implied through the defaults ('default today, US Eastern') and the accepted destination forms, which tells the agent how to call it. There is no explicit when-to-use or when-not guidance relative to the two sibling deadline tools, so the agent must infer the distinction.

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

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

The annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds real context beyond that: the deadline target is fixed at December 25, the scope is exactly one ZIP, and the valid prefix ranges are enumerated. It does not say what happens for an out-of-range ZIP, which keeps it from a 5.

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 sentence, front-loaded with the outcome (send-by dates for December 25), followed by the input restriction and covered mail classes. Every clause carries information; there is 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?

For a single-parameter read-only lookup with no output schema, the description is nearly complete: it establishes the deadline, the input domain, and the mail classes returned. The only gap is that it does not characterize the response (e.g., a date per mail class), which would help an agent know what to expect.

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% and the single parameter is documented, so the baseline would be 3. The description earns an extra point by constraining the value semantically, tying the ZIP to APO/FPO/DPO prefixes (090-099 AE, 340 AA, 962-966 AP) rather than the schema's bare examples.

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 the exact resource (USPS holiday send-by dates for December 25 delivery), the constrained input domain (one APO/FPO/DPO ZIP code with prefixes 090-099 AE, 340 AA, 962-966 AP), and the four mail classes covered. That APO/FPO/DPO scoping implicitly separates it from the general-purpose siblings check_holiday_ship_by_date and get_usps_holiday_shipping_deadlines.

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 scope: a military-mail ZIP in the listed ranges means use this tool. However, there is no explicit when-to-use/when-not statement and no sibling tool is named as the alternative for domestic or non-APO ZIPs, leaving the routing decision to inference.

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

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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. The description adds real value beyond them: data is read live from usps.com at call time (implying freshness, no cached snapshot), it is scoped to the current holiday season, and each entry includes days remaining from today — useful for reasoning about urgency.

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 core fact (send-by dates for delivery before Dec 25, current season) is front-loaded, and the long service/region enumeration is genuinely informative rather than filler. It is a single dense sentence that is harder to scan than a short list would be, but every clause contributes scope information.

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 carries the burden of describing the return value, and it does so by naming the service tiers, world regions, APO/FPO/DPO ZIP groups, and the derived days-left field. Formatting and cardinality of the response are unstated, but for a static reference lookup the agent has enough to call it correctly and know what it will get.

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 tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. No parameter-level clarification is needed or missing.

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 scope: USPS recommended send-by dates for delivery before December 25, read from usps.com for the current season. It enumerates the exact service tiers and destination groupings covered, so an agent knows precisely what table this returns. It does not explicitly name the sibling tools (check_holiday_ship_by_date, get_military_mail_deadline) or contrast itself with them, which keeps it short of a 5.

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?

There is no when-to-use or when-not-to-use guidance and no routing to alternatives. The description implies a reference lookup for current-season deadlines, but with two sibling tools covering overlapping ground (date-based checking and military mail), the agent is left to infer which one answers a given question.

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