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

The readOnlyHint annotation already covers the read-only nature. The description adds only the source/scope ('from the market-data provider') and does not disclose return format, ordering, or whether the list is exhaustive. This is acceptable but minimal.

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 a single, front-loaded sentence with no filler. It delivers the key action and resource immediately and earns its place without redundancy.

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 no-parameter, read-only enumeration tool, the description is nearly complete: it explains what is returned (coin symbols). It would be slightly stronger if it noted that the returned symbols can be used as inputs to market_* tools, but nothing critical is missing for correct invocation.

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?

The tool has zero parameters and the schema has 100% coverage, so there are no parameter semantics for the description to add. The baseline for a no-parameter tool is 4, as nothing is missing here.

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 states a specific verb ('Lists') and a specific resource ('coin symbols available from the market-data provider'). It clearly distinguishes this tool from siblings like market_coin_details, which provide details about individual coins rather than enumerating supported symbols.

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 implies the tool is used when you need the list of supported coin symbols, but it gives no explicit guidance about when to choose this tool over alternatives. It does not mention exclusions or point to related market tools such as market_quotes or market_candles.

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