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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds the genuinely non-obvious behavioral rule: real-time only for symbols on the key's real-time watchlist, otherwise a price at least 15 minutes old. That data-freshness caveat is exactly the kind of context annotations cannot express. The trailing 'Pro.' fragment hints at a subscription-tier gate but is too terse to be actionable.

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?

Front-loaded with the resource and its freshness semantics, then the example query, in three short sentences. The dangling 'Pro.' is a wasted fragment that a reader cannot reliably interpret.

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 no output schema, the description is the only place an agent could learn what the call returns, and it says only 'latest price' — no indication of fields, error behavior for unknown tickers, or whether the delayed/real-time distinction affects output shape. Adequate to call correctly, but thin for a tool with no output contract.

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 coverage is 100% for the single ticker parameter, so the schema already carries the format guidance (NVDA, SPY, BRK.B). The description adds no syntax or edge-case detail beyond it, making the baseline 3 appropriate.

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?

States a specific verb+resource ('Latest price for a stock or ETF') and the scope is narrow enough to separate it from stock_candles, stock_news, and technical_indicator without opening a schema. It does not explicitly name a sibling tool, so it stops short of a 5.

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?

Provides a concrete invocation scenario ('Use for "what is NVDA trading at?"'), which makes the intended use unambiguous. It gives no when-not guidance and does not route to alternatives such as stock_candles for historical data.

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