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

Annotations already cover read-only and non-destructive behavior, but the description adds real operational context: a 36-country coverage limit, a 2015 normalization baseline, tier-gated response fields (paid plans add 1/3/6/12-month changes, high/low/average), and an explicit 2-credit cost. It stops short of describing failure modes for unsupported country codes or what the free-tier payload looks like exactly.

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 definition is front-loaded with purpose and coverage, then moves to input, then output, then cost. The only waste is the redundant 'Global Stock Market: Global Stock Market tracks' echo of the title, and the single long sentence is dense but readable.

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 an output schema present, the description does not need to enumerate return fields, yet it helpfully summarizes the tier-dependent payload and discloses credit cost. For a 4-parameter read-only lookup this is nearly complete; only error/edge-case behavior for unsupported countries is missing.

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%, so the baseline is 3. The description restates the two-letter country code input and implies that the history-style monthly readings are tied to paid plans, but it adds no format or constraint detail beyond the schema for year/month/history.

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 states a specific verb and resource: tracks share-price indices for 36 countries on a normalized 2015 baseline. That is far more concrete than 'get stock data' and lets an agent tell it apart from company-level siblings like StockExchange or TickerSymbols, though it never explicitly names those alternatives.

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 imperative 'Send a two-letter country code to receive...', and the country-level scope hints that this is not a per-ticker tool. However, there is no explicit when-to-use vs. when-not guidance and no reference to the closely related siblings (StockExchange, StockMarketOpenTimes, TickerSymbols).

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