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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds no behavioral context of its own beyond a pricing boilerplate block: it says nothing about granularity constraints, rate limits, or result volume, which are the traits that actually matter for this 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?

The core is a single front-loaded sentence that puts the resource and key first, and the pricing block is a mandated disclosure rather than filler. The 'This endpoint allows you to...' framing is mildly wasteful but costs one clause, not a paragraph.

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, and annotations cover the safety profile. What is missing is the operational constraint tying 'days' to 'interval' granularity (e.g. that hourly data is only available over short windows), which an agent needs to avoid a failed or misleading call.

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%, and all five parameters carry either a description or an enum, so the schema does the heavy lifting. The description only restates that the call is keyed on coin ID, adding no syntax or format meaning beyond the schema. Baseline 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?

The description names a specific verb (get) and a precise resource (OHLC chart: Open, High, Low, Close) keyed by coin ID, so the agent knows exactly what data comes back. It does not, however, distinguish this from close siblings such as get_coingecko_coins_id_market_chart or get_coingecko_coins_id_history, leaving the agent to infer that 'OHLC' is the differentiator.

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 when-to-use, when-not-to-use, or alternative-naming guidance. An agent choosing between this, market_chart, and history gets no routing help, and there is no mention of the interval/days interaction that governs whether the call is even valid.

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