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

Annotations already cover the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true), and the description adds real behavioral context: no card is charged, the payment type is recorded before the invoice is marked paid, Kickserv does not zero the balance on its own, human confirmation is required, and a Cotlet API key with app access is needed.

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, but the description wastes space on near-verbatim repetition: 'No card is charged' appears twice and the human-confirmation instruction is stated twice ('By default you confirm each call' and 'Reaches other people: confirm with the user before each call'), so not every sentence earns its place.

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?

For a write tool with annotations covering safety and no output schema, the description covers the key gaps: it clarifies the no-card-charge nature, the mark_paid sequencing, the balance caveat, and the confirmation/auth requirements. Only the absence of any sibling comparison keeps it from being fully complete.

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 100%, so the schema already documents all five parameters. The description reinforces mark_paid semantics ('marks the invoice paid when mark_paid is true') but adds no syntax, format, or constraint beyond what the schema states, so the baseline of 3 applies.

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?

States a specific verb and resource ('Log a manual payment ... on a job and mark the invoice paid') and scopes it to manual payments with 'No card is charged', which separates it from card-charging siblings like kickserv_add_charge and kickserv_generate_invoice.

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?

Provides contextual guidance ('confirm with the user before each call', 'By default you confirm each call; you can switch that off for this tool'), which is genuinely useful. However, it never names an alternative tool or a condition for choosing this over another payment/charge path, so usage is only implied.

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