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

Annotations already declare the mutation/idempotency profile, yet the description adds genuinely new behavior: exact price, the payment endpoint the client must hit, and the fact that webhook_url and topics are echoed to the client to enable retry. One tension: it directs a POST to an external https endpoint while openWorldHint=false, though this is arguably the client's action, not the tool's.

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?

Five short sentences with no filler; the price and non-creation caveat land early. The ordering is slightly jumbled (price before purpose correction, payment URL before echo semantics), but nothing is padding.

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?

With an output schema present, return values need not be explained, and the description covers cost, payment target, and echo behavior. However, it omits the relationship to list_alert_topics for discovering valid topic ids and says nothing about invoice/payment expiry versus the 30-day subscription term, leaving an agent to guess the follow-up flow.

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 baseline is 3, but the description adds the concrete allowed topic ids (sdk-security, lightning-releases, lightning-wallets, protocol-specs), which the schema only describes as 'Required topic ids.' It also explains why webhook_url/topics are echoed, which gives the webhook_url parameter retry semantics not present in the schema.

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 states a concrete outcome: it returns payment info (2000 sats / 2.00 USD) for a 30-day signed webhook, and explicitly clarifies 'This tool does not create the subscription,' which corrects an agent's likely assumption from the name create_alert. It does not explicitly differentiate itself from siblings such as list_alert_topics or check_payment_endpoint, but the verb+resource is specific enough to act on.

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 implies the workflow ('Pay POST https://api.agentpaywire.com/v1/alerts') and rules out one expectation ('does not create the subscription'), but never states when to prefer this over list_alert_topics (to discover valid topics) or check_payment_endpoint. Usage must be inferred from the payment instructions rather than declared.

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