get_rune_balances

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

No annotations exist, so the description carries the full burden and does reasonably well: it names the backend indexer, discloses a rate limit (5 req/s on free tier) and the API-key requirement for higher limits, and describes the returned fields. It stops short of stating pagination behavior for addresses with many runes or what happens on indexer failure.

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?

Four short sentences, front-loaded with the operation and scope, then return fields, then defaults. The trailing 'Tip' cross-selling `earning_opportunities` is marginally promotional but short enough not to displace the core content.

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 one-parameter read tool with no output schema, the description covers the data source, return fields, default-address behavior, and rate limits. The main residual gap is pagination/large-result handling, but nothing an agent needs in order to call it is missing.

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% for the single `address` parameter and its default is already documented in the schema. The description restates the same default, adding no new syntax, format, or validation detail beyond what the structured field provides.

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 and resource ('Fetch all rune token balances held at a Bitcoin address') plus the data source (Unisat indexer). It is clear on its own, but does not distinguish itself from the very similar sibling `runes_get_address_balances` in the tool list.

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?

Gives concrete fallback behavior ('If no address is provided, uses the active wallet's Taproot address') and an API-key tip for rate limits, which is genuinely useful context. However, with near-duplicate siblings like `runes_get_address_balances` and `get_rune_utxos` available, it offers no explicit when-to-use or when-not-to-use guidance.

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