stock_extended_hours

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

Annotations declare readOnlyHint=true, but the description goes far beyond: explains the most recent valid print per session window, null behavior for post_market during regular hours, weekend/holiday behavior, and computed % changes. This gives agents a precise mental model of the tool's 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.

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

Well-structured with a purpose statement, usage context, behavioral notes, and a clear Returns bullet list. No wasted sentences; every part adds value and the text is front-loaded with the most important info.

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?

The description is thorough for a one-parameter tool with no output schema. It documents return fields, null handling, session windows, and holiday behavior. It fully covers what an agent needs to know to invoke and interpret results correctly.

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?

With 0% schema description coverage, the description compensates by explaining the symbol parameter with examples (AAPL, NVDA, TSLA, SPY, ^GSPC) and limiting to US symbols. It does not exhaustively cover edge cases like crypto or international formats, but for this simple param it is adequate.

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 opens with a specific verb+resource: 'Real-time pre-market and after-hours prices for a US stock symbol.' This clearly distinguishes it from sibling tools like yahoo_price or stock_prices, which likely focus on regular hours. Use-case examples further cement its purpose.

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?

Explicitly tells when to use: 'when the user asks about a stock outside the regular 9:30am-4pm ET session' with concrete scenarios. It implies not to use for regular hours but does not name alternate tools directly. Clear context, but lacks explicit alternatives or exclusions.

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