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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds two genuinely useful facts beyond that: the metric is computed on daily returns, and a Growth-or-higher plan is required. It says nothing about data freshness, lookback limits, or how missing/illiquid currencies are handled.

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, zero filler, with the metric and scope front-loaded before the access requirement. Every clause carries information an agent can act on.

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 four-parameter read-only computation with full schema coverage and clear annotations, the definition covers what is computed, over what window, and the plan gate. The main remaining gap is the return shape (e.g., a coefficient per currency), which is unstated and there is no output schema to compensate.

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 each parameter (to, from, base, currencies) is documented in the schema with formats and defaults. The description restates the window and base-currency concepts but adds no syntax, constraints, or edge-case meaning beyond the schema, so the 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 computation ('correlation of each currency's daily returns with a base currency's') and a scope ('over a window'), which is enough to distinguish it from siblings like analyze_volatility or analyze_drawdown without opening the schema. It does not explicitly contrast with any sibling, which keeps it from 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?

No explicit when-to-use or when-not-to-use guidance relative to alternatives is given; usage is implied by the statistical concept. The one concrete gating statement, 'Growth plan or higher,' tells the agent about an access precondition but not about tool selection.

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