send_to_username

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

With no annotations, the description carries the full burden, and it does add real value by disclosing that the transfer is intraledger, free, and instant, plus that a wallet lookup happens server-side. It omits critical behavioral facts for a money-moving operation: irreversibility, what happens if the username is unknown or the balance is insufficient, and any auth requirements.

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 with zero filler, and the identifying behavior (username-based intraledger send) is front-loaded before the cost/speed 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?

Incorrect on reflection — for a fund-transfer tool with no annotations and no output schema, the omission of failure modes and irreversibility is a genuine completeness gap; the description covers the happy path only.

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 all five parameters including units and the currency enum are already documented. The description adds no parameter-level meaning beyond confirming the recipient is identified by username; baseline 3 is appropriate.

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 names a concrete verb and resource ("Send Bitcoin to a Blink user by their username") and adds that it is an intraledger transfer, which distinguishes it from on-chain and Lightning-address payments among the siblings. It stops short of naming the closest alternative (send_to_wallet) explicitly, so the differentiation is implied rather than stated.

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 implies the selection condition — use this when you know the recipient's Blink username rather than their wallet or address — but never states when to prefer it over send_to_wallet, pay_lightning_address, or lookup_user_wallet. There are no exclusions, prerequisites, or fallback guidance.

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