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

Annotations already flag destructive=true and idempotent=true, so the safety profile is partly covered, but the description adds substantial non-obvious context: never request card numbers/CVC/passwords/OTPs, pending checkout is not credit, only the signed Stripe webhook credits funds, retry with the same key, and native card support is host-dependent. It does not contradict any annotation.

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 purpose is front-loaded and most sentences carry behavioral or security value, but the text is dense and repetitive: the 'not native UI/MCP elicitation' point is made twice, and several statements restate schema descriptions. Tighter editing would preserve the content in fewer sentences.

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 must carry return semantics, and it does: card_checkout returns a Stripe hosted-checkout URL, request_challenge returns approval metadata, and the 402 payload carries amount/currency/seller profile. For a payment mutation with annotations, nothing essential is missing.

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 86% schema coverage the baseline is 3, but the description goes beyond the per-field schema text by explaining cross-parameter workflow: when payment_approved is legitimate, when to omit shared_payment_token and use request_challenge, and that request_challenge returns 402 metadata rather than elicitation. This adds genuine inter-parameter meaning.

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 opening sentence states a specific verb and resource ('Request purchased Skysay calling credit for the authenticated workspace') and the title reinforces it. No sibling tool covers wallet top-ups, so there is no ambiguity to resolve, and the description names account_overview as the prerequisite read.

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 explicitly says to read the wallet currency via account_overview first, that owner approval of the exact amount/currency/purpose must precede payment_approved, and that OAuth scope consent is not purchase approval. It also distinguishes the two methods (card_checkout vs shared_payment_token) with the conditions for each.

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