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

Annotations already declare the safe-read, idempotent, closed-world profile, so the bar is lower. The description adds genuinely non-obvious context beyond them: the view key can read but never spend, and it is discarded after the call, which materially informs the privacy/security tradeoff of invoking this tool.

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?

Front-loaded with the core purpose, then scoping, then exclusions, then returns, then a security note. Every sentence earns its place and there is no filler.

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?

With no output schema, the description compensates by naming the return fields (balance_xmr, unlocked_xmr, pending_xmr, scanned_to_height, chain_tip, complete). Combined with usage, exclusions, and view-key handling, an agent has everything needed to call and interpret this correctly.

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%, so the schema already documents address, view_key, and lookback_days. The description reinforces the view-key semantics and the scan-window concept (scanned_to_height) but adds no format or constraint detail beyond what the schema provides, 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?

States a specific verb+resource (balance for one Monero address) and enumerates exactly what is returned (total, unlocked, pending XMR, scanned window, completion flag). It is clearly distinguishable from the sibling read tools by naming the two it is not (xmr_verify_payment, xmr_merchant_report).

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?

Explicit 'When to use' clause covers the two real scenarios (checking holdings now, checking whether funds unlocked) and a 'Do not use' clause routes the agent to the correct alternative for payment proof and history. Nothing is left to inference.

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