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

Annotations already mark this as a non-read-only, open-world, non-destructive write, but the description adds real value: that it reaches tripmates, that confirmation gating applies by default and can be toggled, and that a Cotlet API key with app access is required. It does not describe failure behavior, keeping it from a 5.

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-loaded with the core action and no wasted preamble. The confirmation guidance is stated twice in slightly different words ('By default you confirm each call' / 'confirm with the user before each call'), a minor redundancy.

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 7-param mutation with no output schema, it covers the important unknowns: auth requirement, confirmation workflow, and the cross-user side effect of splitting. Error handling and the shape of the return are unaddressed, but nothing critical to correct invocation 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?

Schema coverage is 100%, so the baseline is 3, and the description adds meaning beyond it by clarifying the social consequence of split_with ('the app shows who owes whom') and the today-by-default date. The other five parameters are left entirely to the schema.

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 an expense') plus distinguishing scope features (currency paid in, optional split between tripmates). An agent can separate this from sibling wanderlog_list_expenses without opening either 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?

Explains when split_with applies and that confirmation is on by default but configurable, plus the requirement to confirm before calls that reach others. It stops short of naming a sibling alternative, but the usage context is clear.

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