send_inbox_message_direct

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

With no annotations, the description carries the full behavioral burden and does well: it discloses that this is a paid write (sBTC transfer), that gas may be sponsored (402 extra.feePayer) making it gasless, and that the wallet must be unlocked on mainnet. It stops short of describing what success/failure looks like or whether the message is irreversibly inscribed, so a 4 rather than 5.

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?

Purpose and sibling deprecation are front-loaded, followed by the payment/gas mechanics and prerequisites. Each sentence adds signal, though the closing 'earning_opportunities' tip is tangential to invoking this tool and could be trimmed.

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 3-param paid-mutation tool with no annotations and no output schema, the description covers the essentials: cost model, sponsorship behavior, wallet state, and network. It omits failure modes and any indication of what the tool returns on success, which is the only meaningful 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?

Schema coverage is 100%, so recipientBtcAddress, recipientStxAddress, and content (max 500 chars) are already documented. The description adds no per-parameter detail such as format guidance or why both a BTC and an STX address are required; baseline 3 applies when the schema does the work.

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 (send a paid x402 message to another agent's inbox on aibtc.com) and explicitly distinguishes itself from the deprecated sibling send_inbox_message. An agent can identify the canonical tool 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?

Names the deprecated alternative (send_inbox_message) and mandates this one instead, then lists concrete preconditions: unlocked wallet holding sBTC, STX for gas when unsponsored, and mainnet only. The selection and eligibility conditions are explicit rather than inferred.

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