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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses the two behaviors an agent would otherwise trip over: the first call returns x402 PaymentRequired and must be retried with _meta['x402/payment'], and success carries _meta['x402/payment-response']. It also defines the null-SL/TP safety condition, which is a genuine behavioral constraint not encoded anywhere else.

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?

Four sentences, front-loaded with the decision purpose, then output shape, then the null-guard rule, then the payment mechanics. No filler and no repetition of the title's 'Buy and get' phrasing.

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?

There is no output schema, so the description carries the return-value burden and does so fully — signal, entry, SL/TP, strength, diagnostics. Combined with the payment protocol notes and the null-handling rule, an agent has everything needed to call it and interpret the response.

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?

With zero schema properties the baseline is 4, and this description earns the extra point by documenting the implicit _meta['x402/payment'] argument that the input schema (additionalProperties: false, empty properties) does not expose at all. An agent could not construct the retry call correctly from the schema alone.

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 opens with a specific verb and resource: 'Decide whether to open, avoid or manage a BTC 4H trade.' It then enumerates the exact return values (LONG, SHORT, NEUTRAL/NO TRADE, Entry, SL, TP, setup strength, diagnostics), which makes the tool's output contract unmistakable. The BTC/4H specificity distinguishes it from the ETH, XRP, ONDO and TZ-select siblings without needing to name 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 decision context (open/avoid/manage) and gives an explicit action rule: 'If SL or TP is null, do not open a new position.' It also explains the payment retry loop. It stops short of routing the agent to alternatives — notably prepare_btc_4h_purchase, whose relationship to this tool's x402 flow is left implicit.

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