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

The annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is fully covered. The description's contribution is describing the returned content (level, change, recent daily history), which is useful since there is no output schema, but it says nothing about caps, freshness or the meaning of the 'change' field (absolute vs percent, daily vs period).

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?

A single sentence that front-loads the returned data and ends with the enumerated resource values. There is no filler, and nothing an agent needs for basic selection is buried.

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 two-parameter read-only index lookup with no output schema, the description covers the essential shape of the response (level, change, daily history). It falls short only on sibling disambiguation and on what the 'change' value measures, which matter more here because several Korean-market siblings exist.

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 description coverage is 100%: the index enum is fully enumerated and days carries a default of 5 and max of 60. The description repeats the index values but adds no further semantics for days or how it interacts with the history returned. Baseline 3 applies when the schema does the heavy lifting.

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 resource precisely (a Korean market index: KOSPI, KOSDAQ or KOSPI200) and the data returned (level, change, recent daily history). It is clear enough for an agent to know exactly what it fetches, but it never distinguishes itself from siblings like kr_quote or kr_price_history, which cover overlapping quote/history concepts.

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 explicit when-to-use or when-not-to-use guidance. Given sibling tools kr_quote, kr_price_history, kr_investor_flows and kr_top_by_market_cap, an agent must infer that kr_index is for indices rather than individual stocks, which is only weakly implied by naming KOSPI/KOSDAQ/KOSPI200.

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