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

With no annotations, the description carries the burden and does well: it discloses that funding is a real BSV payment signed by a wallet, that it occurs externally on the website, and that the returned key is used as 'Authorization: Bearer channelId:channelSecret' or apiKey. It does not say precisely what calling the tool itself returns or whether it is idempotent.

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 tight sentences: the first states purpose, the second front-loads the critical constraint (payment happens elsewhere) and the follow-up credential format. 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?

For a zero-parameter instructional tool with no output schema, the description covers the essential flow: pay on the website, receive a channel key, present it as a bearer token. Minor gaps remain around what the call itself returns and error behavior, but an agent can act correctly on what is given.

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?

The tool takes zero parameters, so the baseline is 4 and the schema has nothing to clarify. The mention of 'apiKey' refers to credential usage on subsequent calls rather than a parameter of this tool, which is slightly ambiguous but not misleading.

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?

The description uses a specific verb and resource ('Explains how to open + fund a prepaid channel') and makes clear that the tool returns instructions rather than performing the funding. It is distinguishable from siblings like channel_balance and infer, though it never explicitly names them.

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?

It states the key usage constraint (funding happens once, at the website, not through this call) and how to use the resulting credential, so usage is implied. But it never says when an agent should invoke this tool versus going straight to infer or x402_infer, nor what triggers the need for a channel.

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