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 customer is issued a unique Pay@ bill payment code and notes that the amount excludes Pay@ merchant fees. However, it does not clarify whether the operation has side effects, requires prior wallet setup, or what the JSON response contains. The dangling 'All payments' fragment adds ambiguity.

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 redundant: 'Returns a payment reference for use with Pay@' appears twice, and there is an incomplete sentence 'All payments'. While the @param block is organized, the prose lacks conciseness and structure, making the description longer than necessary without adding clarity.

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?

The description covers the funding flow, usage venues, and parameter meanings, and an output schema exists to explain return values. However, the repetitive text, the incomplete 'All payments' sentence, and the lack of behavioral context (e.g., side effects, prerequisites) leave it adequate but not fully complete for a 5-parameter tool with no annotations.

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?

The description adds significant value beyond the bare schema (0% schema description coverage) by explaining all 5 parameters: api_key, token source, account_fk constraints (database ID, not 0, from /wallet/accounts_list), amount meaning, and reference purpose. This fully compensates for the schema's lack of descriptions.

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 'Returns a payment reference for use with Pay@', specifying a concrete verb and resource that distinguishes it from sibling funding tools like fund_banks or fund_card_quote. However, the repetition of the same statement and an incomplete sentence ('All payments') slightly muddy the clarity.

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 provides clear context: 'Customer uses this payment reference to fund via Pay@ online (South Africa) or at Pay@ supporting retailers in South Africa and Botswana.' This implies when to use the tool, though it does not explicitly mention alternatives or when not to use it.

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