btc_balance

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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds genuine value beyond that by naming the external data source (blockchain.info) and scoping the result to balance only, not transaction history — relevant for an open-world network call.

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, and the core purpose is front-loaded ahead of the disambiguating scope note.

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 usefully specifies the return unit (satoshi), which is exactly the missing context an agent needs. It doesn't mention error behavior for invalid addresses or rate limits from the external provider, leaving a small gap.

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?

Only one parameter, and the schema fully documents it ('Bitcoin address' with length bounds). The description adds no parameter-level guidance beyond the schema, so the baseline of 3 for high schema coverage 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, unit (satoshi) and upstream source (blockchain.info), and implicitly distinguishes itself from transaction-history siblings with 'without full transaction history'. An agent can identify this as a lightweight balance-only lookup without opening the schema.

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?

'Quick balance check without full transaction history' gives clear usage context and hints at the alternative (transaction-listing tools like btc_tx). It doesn't name a sibling explicitly or state when-not-to-use, so it falls short of the 5 mark.

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