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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and openWorld, so safety is covered. The description adds real value beyond them by disclosing a data-availability boundary ('History starts on 24 August 2026, when recording began'), which warns an agent that older windows will be sparse or empty. It does not say anything about sampling granularity or the shape of the series, which keeps it below a 5.

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 with no filler, and the core comparison is front-loaded ahead of the window/history caveats. The telegraphic fragment 'both sides.' and the redundant re-listing of window values cost it a little polish.

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 single optional-parameter, read-only tool with no output schema, the description covers scope and data availability but never describes what comes back (a premium series, percentages vs. absolute values, per-side fields). The return-value gap matters precisely because no output schema exists 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 the schema already documents the window parameter, its default of 7d, and the allowed values with an example. The description only restates that same enumeration, adding no new meaning such as whether windows are calendar-aligned or rolling. 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?

States a concrete verb+resource: it compares Haveno peer-to-peer quotes against centralized spot price over time, and 'both sides' signals it returns both buy and sell premiums. 'Over time' also separates it from snapshot siblings like haveno_book and haveno_payment_methods, though the phrasing ('premium' is never actually used) leans on jargon an agent must infer.

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 and no sibling is named as an alternative, despite five haveno_* siblings existing. The only guidance is the window enumeration and a data-availability note, so an agent must infer that this is the historical time-series counterpart to haveno_book.

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