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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds the meaningful trait that data is real-time and which fields come back, but says nothing about failure modes for invalid tickers or the rate limits that come with a Finnhub free-tier API key.

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?

Two short sentences, capability front-loaded, and nothing extraneous. The example is mildly redundant with the schema's examples array, which keeps it from a 5.

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?

An output schema exists, so return values need not be explained, annotations cover safety and idempotency, and the schema fully documents both parameters. For a simple two-param read tool the description is sufficient, with only operational caveats (invalid symbol behavior, API-key/quota limits) left unstated.

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 both symbol and _apiKey are already documented in the schema, including ticker examples and where to obtain the key. The description's example repeats the schema's own examples rather than adding new semantics; baseline 3 is 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 and resource ("Get a real-time stock quote") and enumerates the returned fields (price, change, volume), so the agent knows exactly what it produces. It does not distinguish itself from the sibling search_symbol, which is the obvious adjacent tool for symbol resolution.

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 guidance on when to use this versus alternatives such as search_symbol (symbol lookup) or get_company_news/company_facts, nor any prerequisites. The inline example shows how to call it but says nothing about selection conditions or when-not to use it.

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