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

No annotations are provided, so the description carries full disclosure burden. It mentions the $0.005 USDC per call cost, which is useful. However, it doesn't describe the response format, whether data is historical capped, data granularity per range, or any rate limits. For a data-fetching tool with zero annotations, this is a meaningful gap.

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 compact sentence that packs the cost, resource type, and supported ranges efficiently. It's front-loaded with the cost disclosure. Minor waste: the enumerated day values duplicate what's in the schema's days description, but this is lightweight.

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 data-retrieval tool with 3 params and full schema coverage, the description covers the core need: what data, what ranges, and cost. However, with no output schema and no annotations, it omits return format (candle structure, OHLC fields), which could be ambiguous. Acceptable but not thorough.

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 context by enumerating valid 'days' values (1, 7, 14, 30, 90, 180, 365) which reinforces the schema's vague '1 | 7 | ...' list. It doesn't add format/syntax details for 'id' or 'vs' beyond schema, but the schema already covers these with examples.

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 verb+resource: 'OHLC candlestick data for any CoinGecko coin id' with specific time ranges enumerated. It distinguishes this from siblings like 'price' (current) and 'market_summary' by specifying it's historical candle data. However, it doesn't explicitly contrast with siblings, so not 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?

The description implies it's for retrieving candlestick data but gives no when-to-use guidance or exclusions. It doesn't mention that 'price' might be better for current spot prices or when one might prefer different ranges. The supported range values (1-365 days) are listed, providing some guidance, but no explicit alternatives are named.

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