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

With no annotations, the description carries the full burden of behavioral disclosure. It discloses the required prerequisite ('Requires a Finnhub API key to be configured on the server'), the real-time nature, and the specific return fields. It doesn't mention rate limits or error handling, but for a read-only quote tool, this is reasonably transparent. The description adds context about what data is returned (current price, intraday high/low, etc.) beyond what the schema covers.

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 description is structured with a clear lead sentence, then return fields, usage scenarios, exclusions, and prerequisites. It's somewhat verbose (4-5 sentences) but every sentence adds useful information. It front-loads the primary purpose and then provides actionable guidance. No unnecessary fluff.

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 tool with 2 parameters and no output schema, the description is remarkably complete. It covers purpose, return data, use cases, alternative tools, exclusions, and a prerequisite. It gives the agent enough context to decide when to use this tool and what to expect from it.

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%, so baseline is 3. The description adds value by explaining the 'symbol' parameter with concrete examples (AAPL, MSFT, etc.) and clarifies the 'include_company_info' parameter's default behavior ('Defaults to true') and when to set it false. It also contrasts with stock_price_lite to help understand parameter usage.

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 clearly states the tool's function: 'Retrieves real-time stock price quotes and company information for any publicly traded company via the Finnhub API.' It specifies the verb (retrieves), resource (stock quotes and company information), and scope (any publicly traded company). It also distinguishes itself from sibling tools like stock_price_lite and crypto_price by outlining its unique value.

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?

The description provides explicit usage guidance: 'Use stock_quote when an agent needs to look up a stock price...' and 'Prefer stock_quote over stock_price_lite when the agent needs price change...' It also gives negative guidance: 'Do not use for cryptocurrency prices — use crypto_price...' and 'Do not use for fiat currency conversion — use currency_convert...' This clearly delineates when to use this tool versus alternatives.

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