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

With no annotations, the description carries the full burden and does well: it discloses the two auth paths, the exact error envelope (isError "error: <code> (<status>): <message>"), and the specific failure codes no_channel_key and invalid_channel with their 401/404 causes (not found, bad secret, closed). It stops short of stating that the call is read-only or whether it consumes quota.

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 sentences, front-loaded with what the tool returns, then auth, then error semantics. Dense but every clause carries information; the error-code parenthetical is slightly compressed but earns its place.

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?

No output schema exists, and the description compensates by enumerating the returned fields (balance, spend, request count) and the failure contract. An agent could call this correctly from the description alone; only quota/rate-limit and read-only status are unaddressed.

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% and the single parameter already documents the channelId:channelSecret format and the 'omit to use Authorization header (preferred)' rule. The description's auth sentence largely restates that, adding no new syntax or format detail, 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 (check) and resource (prepaid channel balance) plus the exact fields returned: remaining Bitcoin BSV balance, spend, and request count. The resource is clearly distinct from siblings like open_channel or infer, though no sibling is named explicitly.

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?

The description covers the auth choice (Authorization header preferred over apiKey) but never says when to reach for this tool versus open_channel or the infer variants, nor any preconditions beyond having a channel key. Usage is implied rather than stated.

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