tossinvest-mcp

Get market trading hours

tossinvest_get_market_calendar

Read-onlyIdempotent

Check Korean or US market trading hours for the previous, current, and next business days. Use it to see if the market is open, when it opens, or why an order was rejected outside trading hours.

Instructions

Get trading-session hours for the Korean or US market across three business days: previous, current and next.

Use this to answer "is the market open?", "when does it open?", or to explain an order-hours-closed rejection. All times are ISO 8601 in KST (+09:00) for BOTH markets — US session times are already converted to Korean time.

Args:

country ('KR' | 'US'): which market.
date (string, optional): YYYY-MM-DD reference date. Omit for today. For US, this is the US local date.
response_format ('markdown' | 'json'): default 'markdown'.

Returns { country, previousBusinessDay, today, nextBusinessDay }, each { date, ...sessions }.

KR: an 'integrated' object (KRX + NXT combined) holding preMarket / regularMarket / afterMarket, each { startTime, endTime }. After-hours single-price and closing-price sessions are excluded.
US: dayMarket, preMarket, regularMarket, afterMarket, each { startTime, endTime } or null. On a holiday all four are null.

Errors: none specific; an invalid date format returns 400 invalid-request.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`date`	No	Reference date (YYYY-MM-DD). Omit for today.
`country`	Yes	'KR' for the Korean market (KRX/NXT), 'US' for the US market.
`response_format`	No	Output format: 'markdown' for a compact human-readable summary, 'json' for the complete raw payload.	markdown

Output Schema

TableJSON Schema

Name	Required	Description
`today`	No
`country`	Yes	KR or US
`nextBusinessDay`	No
`previousBusinessDay`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Sep 8, 2026

TDQS

A5/5.0

Behavior5/5

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

The description discloses critical behavioral traits beyond the annotations: all times are ISO 8601 in KST (+09:00) for both markets (US converted), the exclusion of after-hours single-price and closing-price sessions, holiday behavior (all four null), and error handling (invalid date returns 400). These details are not present in the annotations and materially affect how an agent interprets results. No contradiction with 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 structured with clear sections (Args, Returns, Errors) and every sentence contributes necessary information. It front-loads the core purpose and usage before diving into details. There is no filler or redundancy; each line earns its place.

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 complexity (multiple markets, timezone conversion, exclusions, error behavior) and the presence of an output schema, the description fully equips an agent to call it correctly. It explains the return structure, the exact fields for each market, the meaning of nulls, and the error condition. No essential information is missing.

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

Parameters5/5

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

Schema coverage is 100% and each parameter already has a description, but the tool description adds meaningful context: the date parameter is explicitly clarified as the US local date for the US market, and the response_format default is reinforced. The country parameter's meaning (KRX/NXT vs US) is explained in the schema, and the description reiterates the timezone conversion nuance that is not in the schema. This adds genuine value beyond structured fields.

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 states a specific verb ('Get'), a precise resource (trading-session hours), and the exact scope (Korean or US market across three business days: previous, current, next). It is unambiguous and clearly distinct from sibling tools like order management or price queries. The title reinforces the purpose without tautology.

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?

Explicitly states when to use: 'Use this to answer

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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