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

readOnlyHint=true already tells the agent this is a safe read, and the description adds only the underlying REST route (GET /stock/symbol), which doesn't change invocation behavior. Nothing is said about pagination, result size, rate limits, or the shape of what comes back — meaningful gaps for a symbol-enumeration endpoint.

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, purpose front-loaded, no filler. The trailing REST-route reference is marginally useful context but borders on noise for an agent that only needs the tool name.

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 simple, read-only, 4-parameter endpoint with full schema coverage, the essential information is present. However, with no output schema the description should hint at the return format or volume, and it says nothing about result size or pagination for what could be a very large symbol list.

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 all four filters (mic, currency, exchange, securityType) are already documented in the schema with examples and the required flag. The description adds no additional parameter meaning, so the baseline of 3 applies.

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 ('List all symbols supported on an exchange'), which is clearly an enumeration operation rather than a lookup. It is implicitly distinguishable from the sibling finnhub_symbol_search, but the description never names or contrasts with that sibling.

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 phrase 'list all symbols supported on an exchange' implies you use this to enumerate an exchange's universe, but there is no explicit when-to-use, when-not-to-use, or named alternative (e.g. finnhub_symbol_search for name/lookup queries). Guidance is only inferable.

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