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

Annotations provide no hints (all false), so the description carries the full burden. It discloses that it replaces any existing split and explains the equal-split default with rounding. It does not mention failure conditions or authorization needs, but the main behavioral traits are covered adequately for a mutation tool.

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?

Two concise sentences: the first states purpose and the second explains the default behavior and replacement semantics. Front-loaded, no fluff, 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 mutation with no annotations and low schema coverage, the description covers core behavior but lacks details on prerequisites (e.g., transaction must exist and be an expense), error cases, or when to use this vs other tools. The presence of an output schema reduces the need to explain returns, but more operational context would help.

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 low (33%) – only note has a description. The description clarifies that omitted amounts default to equal split, which adds meaning to the optional amount parameter. However, transaction_id and the overall people array structure are not elaborated beyond the schema, so the description only partially compensates for the coverage gap.

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 (split) and resource (transaction), and explains the outcome (each owes their share). It also mentions the key behavior of replacing any existing split, which distinguishes it from siblings like delete_split. Clear and specific.

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 clear context: splitting an expense with other people. The note that it replaces existing splits implies it can be used for updating, but it does not explicitly mention when to prefer this over alternatives like correct_transaction or delete_split. It has a defined context but lacks explicit exclusions or comparisons.

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