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

Annotations already declare readOnlyHint, non-destructive, and openWorld. The description adds real value beyond them: newest-first ordering, the date-range scoping behavior, the returned fields, and the auth requirement ('Needs the user's Cotlet API key with access to this app'). It does not cover pagination or result size limits.

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?

Front-loads the resource well, but the field list ('member, amount, date and reason') is stated twice in the first two sentences, which is pure redundancy. The past-due/total clarification is useful but spread across two separate sentences, diluting the structure.

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?

No output schema exists, so the description carries return-value burden and does a reasonable job: it names the fields, ordering, and the sum-as-total semantics. Auth is covered. Pagination and result-count behavior are the main omissions for a list tool.

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 to/from/location_id. The description mentions the date range but adds no syntax or format detail (e.g., inclusive/exclusive bounds) beyond what the schema provides, so baseline 3 is correct.

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 ('list failed payments') and enumerates the returned fields (member, amount, date, reason). It also explicitly distinguishes itself from a related concept ('not the past-due total'), so an agent can tell what this returns without opening a schema.

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?

Gives clear context — 'Zen Planner marks as failed in a date range' — and rules out confusion with the past-due total, which is a useful exclusion. However, it never points to a specific alternative tool or names the condition that would select one, so it stops short of explicit when-to-use routing.

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