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

With no annotations, the description carries the full burden. It discloses that the paid_tool decorator handles fee debit and stores cost, and that no recomputation is needed. It does not mention side effects or idempotency, but it provides meaningful behavioral insight.

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?

The description is three concise sentences, front-loaded with the core purpose. Every sentence adds value: purpose, behavioral note, and usage context. No redundancy or wasted words.

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?

Given the presence of an output schema and the tool's specific role, the description covers the return value (Schnorr-signed certificate), the calling context, and key behavioral traits. It does not mention error conditions or prerequisites, but overall is complete enough for an agent with access to the output schema.

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 67% (below 80%), so the description should compensate for the missing parameter semantics. However, the description adds no information about parameters; it relies on the schema descriptions already provided. This is insufficient to fully guide parameter usage.

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 clearly states the tool's purpose: 'Certify a purchase order: return a Schnorr-signed Nostr event certificate.' It uses a specific verb and resource, and the context that it is called when a patron purchases credits differentiates it from sibling tools like authority_purchase_credits.

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 explicitly states usage context: 'Called by operator MCP servers (not end users) when a patron purchases credits.' It also notes 'No recomputation needed.' However, it does not explicitly state when not to use it or compare to alternatives, leaving some guidance gaps.

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