OnlineCyberTools MCP (280+ filterable tools)

time_day_of_week

Read-onlyIdempotent

Find the weekday for any proleptic-Gregorian date, list next or previous occurrences of that weekday, or measure the calendar distance between two dates in days and weeks. Supports years from -9999 to 9999.

Instructions

Day of Week Calculator. Find the weekday for any proleptic-Gregorian date, list the next or previous N occurrences of that weekday, or measure the calendar distance between two dates in days and weeks. Select the mode with the operation field (weekday, scan, distance). Use this for weekday lookups and recurring weekday schedules; use time_date_difference when you need business-day counts or to add or subtract a duration from a date. Supports years -9999 to 9999 including BCE (year 0 and negatives), with strict round-trip date validation. Pure local computation: read-only, non-destructive, contacts no external service, and is rate-limited (60 requests/minute for anonymous callers). Returns ISO 8601 date strings plus weekday name, indices, ISO week number, and day-of-year metadata.

Input Schema

TableJSON Schema

Name	Required	Description
`operation`	Yes	Mode: weekday returns the weekday for one date; scan lists N recurring weekday dates; distance measures the gap between two dates.
`year`	No	Year of the date (weekday and scan modes). BCE allowed via 0 and negative values.
`month`	No	Month of the date (weekday and scan modes), 1 to 12.
`day`	No	Day of month (weekday and scan modes); must be a real day for that month.
`count`	No	Scan mode only. Non-zero signed count of same-weekday occurrences; positive scans forward, negative backward.
`fromYear`	No	Distance mode only. Year of the start date.
`fromMonth`	No	Distance mode only. Month of the start date, 1 to 12.
`fromDay`	No	Distance mode only. Day of month of the start date.
`toYear`	No	Distance mode only. Year of the end date.
`toMonth`	No	Distance mode only. Month of the end date, 1 to 12.
`toDay`	No	Distance mode only. Day of month of the end date.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`operation`	No	The operation that was performed (weekday, scan, or distance).
`data`	No	Result payload; fields depend on the operation. Weekday fields shown below; scan adds from/dayOfWeek/count/occurrences, distance adds from/to/days/weeks/weekRemainder/sameWeekday.

Schema Changelog

Changes observed during successful MCP inspections.

Changed21 schema fields changedv0.5.1Jun 3, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

addedInput schema / properties / count

Added value: +{
+  "description": "Scan mode only. Non-zero signed count of same-weekday occurrences; positive scans forward, negative backward.",
+  "maximum": 366,
+  "minimum": -366,
+  "type": "integer"
+}

addedInput schema / properties / day / description

Added value: +"Day of month (weekday and scan modes); must be a real day for that month."

addedInput schema / properties / day / maximum
```
Added value: +31
```
addedInput schema / properties / day / minimum
```
Added value: +1
```

addedInput schema / properties / fromDay

Added value: +{
+  "description": "Distance mode only. Day of month of the start date.",
+  "maximum": 31,
+  "minimum": 1,
+  "type": "integer"
+}

addedInput schema / properties / fromMonth

Added value: +{
+  "description": "Distance mode only. Month of the start date, 1 to 12.",
+  "maximum": 12,
+  "minimum": 1,
+  "type": "integer"
+}

addedInput schema / properties / fromYear

Added value: +{
+  "description": "Distance mode only. Year of the start date.",
+  "maximum": 9999,
+  "minimum": -9999,
+  "type": "integer"
+}

addedInput schema / properties / month / description

Added value: +"Month of the date (weekday and scan modes), 1 to 12."

addedInput schema / properties / month / maximum
```
Added value: +12
```
addedInput schema / properties / month / minimum
```
Added value: +1
```

addedInput schema / properties / operation / description

Added value: +"Mode: weekday returns the weekday for one date; scan lists N recurring weekday dates; distance measures the gap between two dates."

addedInput schema / properties / operation / enum

Added value: +[
+  "weekday",
+  "scan",
+  "distance"
+]

addedInput schema / properties / toDay

Added value: +{
+  "description": "Distance mode only. Day of month of the end date.",
+  "maximum": 31,
+  "minimum": 1,
+  "type": "integer"
+}

addedInput schema / properties / toMonth

Added value: +{
+  "description": "Distance mode only. Month of the end date, 1 to 12.",
+  "maximum": 12,
+  "minimum": 1,
+  "type": "integer"
+}

addedInput schema / properties / toYear

Added value: +{
+  "description": "Distance mode only. Year of the end date.",
+  "maximum": 9999,
+  "minimum": -9999,
+  "type": "integer"
+}

addedInput schema / properties / year / description

Added value: +"Year of the date (weekday and scan modes). BCE allowed via 0 and negative values."

addedInput schema / properties / year / maximum
```
Added value: +9999
```
addedInput schema / properties / year / minimum
```
Added value: +-9999
```

changedInput schema / required

Previous value: -[
-  "operation",
-  "year",
-  "month",
-  "day"
-]New value: +[
+  "operation"
+]

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "data": {
+      "description": "Result payload; fields depend on the operation. Weekday fields shown below; scan adds from/dayOfWeek/count/occurrences, distance adds from/to/days/weeks/weekRemainder/sameWeekday.",
+      "properties": {
+        "count": {
+          "description": "Echoed signed occurrence count (scan mode).",
+          "type": "integer"
+        },
+        "day": {
+          "description": "Echoed day (weekday mode).",
+          "type": "integer"
+        },
+        "dayIndex": {
+          "description": "Weekday index, 0 = Sunday to 6 = Saturday (weekday mode).",
+          "type": "integer"
+        },
+        "dayIndexISO": {
+          "description": "ISO weekday, 1 = Monday to 7 = Sunday (weekday mode).",
+          "type": "integer"
+        },
+        "dayOfWeek": {
+          "description": "Weekday name, Sunday through Saturday.",
+          "type": "string"
+        },
+        "dayOfYear": {
+          "description": "Ordinal day within the year, 1 to 366 (weekday mode).",
+          "type": "integer"
+        },
+        "days": {
+          "description": "Signed calendar distance in days (distance mode).",
+          "type": "integer"
+        },
+        "daysInMonth": {
+          "description": "Number of days in that month (weekday mode).",
+          "type": "integer"
+        },
+        "from": {
+          "description": "Start date as ISO 8601 (scan and distance modes).",
+          "type": "string"
+        },
+        "isWeekend": {
+          "description": "True when the date falls on Saturday or Sunday (weekday mode).",
+          "type": "boolean"
+        },
+        "isoDate": {
+          "description": "The date as a sign-preserving ISO 8601 string (weekday mode).",
+          "type": "string"
+        },
+        "month": {
+          "description": "Echoed month (weekday mode).",
+          "type": "integer"
+        },
+        "occurrences": {
+          "description": "Same-weekday dates as ISO 8601 strings, chronologically ordered (scan mode).",
+          "items": {
+            "description": "An occurrence date in ISO 8601 format.",
+            "type": "string"
+          },
+          "type": "array"
+        },
+        "sameWeekday": {
+          "description": "True when both dates fall on the same weekday (distance mode).",
+          "type": "boolean"
+        },
+        "to": {
+          "description": "End date as ISO 8601 (distance mode).",
+          "type": "string"
+        },
+        "weekNumber": {
+          "description": "ISO 8601 week number (weekday mode).",
+          "type": "integer"
+        },
+        "weekRemainder": {
+          "description": "Leftover days after whole weeks, so days equals weeks times 7 plus weekRemainder (distance mode).",
+          "type": "integer"
+        },
+        "weeks": {
+          "description": "Whole weeks within the distance, truncated toward zero (distance mode).",
+          "type": "integer"
+        },
+        "year": {
+          "description": "Echoed year (weekday mode).",
+          "type": "integer"
+        }
+      },
+      "type": "object"
+    },
+    "operation": {
+      "description": "The operation that was performed (weekday, scan, or distance).",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

First observedv0.1.0May 31, 2026

TDQS

A4.9/5.0

Behavior5/5

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

Annotations already indicate readOnlyHint=true and destructiveHint=false. The description adds valuable context: 'Pure local computation: read-only, non-destructive, contacts no external service, rate-limited (60 requests/minute)'. It also mentions strict validation and BCE support, fully disclosing behavior without contradicting annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise (5-6 sentences) and well-structured: purpose first, then mode explanation, then differentiation, then constraints, then safety/performance. Every sentence provides unique value, no redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity (three modes, 11 parameters), excellent annotations, and an output schema, the description covers all necessary aspects: inputs, modes, constraints, safety, rate limits, and return metadata. No gaps remain.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with descriptions for all 11 parameters. The description goes further by explaining the operation enum and how parameters relate to each mode (e.g., count for scan mode, fromYear/toYear for distance). This adds meaningful semantic context beyond the schema, justifying a slightly above-baseline score.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly labels the tool as a 'Day of Week Calculator' and explains three distinct modes (weekday, scan, distance) with specific verbs like 'Find', 'list', and 'measure'. It distinguishes from sibling tool time_date_difference by specifying when to use each, ensuring no ambiguity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly states when to use this tool ('weekday lookups and recurring weekday schedules') and when to use the alternative time_date_difference ('business-day counts or to add/subtract a duration'), providing clear, actionable guidance.

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

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