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Polygon Io

by io.github.pipeworx-io
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Market Holidays

market_holidays
Read-onlyIdempotent

Return the list of upcoming US stock market holidays from Massive (formerly Polygon.io), including date, holiday name, and exchange status (open/closed/early-close).

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
countYesNumber of items returned.
itemsYesUpcoming market holidays

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changed
    • addedInput schema / examples
      Added value: +[
+  {}
+]
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "properties": {
+    "count": {
+      "description": "Number of items returned.",
+      "type": "integer"
+    },
+    "items": {
+      "description": "Upcoming market holidays",
+      "items": {
+        "properties": {
+          "close": {
+            "description": "Market closing time",
+            "type": "string"
+          },
+          "date": {
+            "description": "Holiday date",
+            "type": "string"
+          },
+          "exchange": {
+            "description": "Exchange code",
+            "type": "string"
+          },
+          "name": {
+            "description": "Holiday name",
+            "type": "string"
+          },
+          "open": {
+            "description": "Market opening time",
+            "type": "string"
+          },
+          "status": {
+            "description": "Market status",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "items",
+    "count"
+  ],
+  "type": "object"
+}
  2. First observed

TDQS

A4/5.0
Behavior3/5

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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is fully covered. The description adds that the data comes from Massive (Polygon.io) and includes a specific field list (date, holiday name, exchange status), which is useful but minimal. It doesn't mention data update frequency or whether early-close is always included, but given strong annotations, this is acceptable.

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 a single, clear sentence that is front-loaded with the main purpose and includes all necessary specifics. No wasted words, perfectly concise.

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

Completeness4/5

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

The tool is simple with no parameters and an output schema exists, so the description doesn't need to explain return values in detail. It covers the key information an agent needs: source, scope (US stock market), and the data included (date, holiday, exchange status). The presence of an output schema also helps. A small gap is not mentioning that the list is 'upcoming' only, but this is stated.

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?

The tool has 0 parameters and schema description coverage is 100% (the schema is empty), so the description carries the full burden. It does a good job by specifying the output fields (date, holiday name, exchange status), which is helpful for the agent to understand what to expect. For a no-parameter tool, the baseline is 4, and the description meets this.

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 states what the tool does: 'Return the list of upcoming US stock market holidays from Massive (formerly Polygon.io), including date, holiday name, and exchange status (open/closed/early-close).' This is a specific verb+resource+scope, and the inclusion of 'upcoming' plus the exchange status details distinguishes it from market_status (which is about live market status) and calendar-related siblings.

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

Usage Guidelines3/5

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

The description implies when to use this tool (when you need upcoming holidays and their exchange status), but it doesn't explicitly state when not to use it or name alternative tools for different holiday/calendar needs. The context signal of sibling tools includes market_status, which could be confused, but the description provides no direct contrast.

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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