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

The readOnlyHint annotation already establishes the safe, non-mutating behavior. The description adds useful context by enumerating the returned data and noting amounts are in the plan's currency, but it does not go deeper into edge cases or response shape. This is acceptable given the annotation coverage.

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 short sentences with no filler. The main action and resource are front-loaded, followed by the specific contents of the response and currency context. 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 simple read tool with one well-documented parameter and a readOnly annotation, the description fully explains what the tool returns and any relevant currency detail. No missing information would prevent an agent from invoking it correctly.

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 input schema already fully documents the single required parameter, including an example and accepted formats. The description adds no additional parameter meaning, but with 100% schema coverage the baseline of 3 is appropriate.

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 states a specific verb and resource: "Read the plan's shared costs (Splitwise tab)", and enumerates exactly what is returned: expenses, each person's balance, and suggested payments. This clearly differentiates it from siblings like add_expense and record_payment, which are write operations.

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 makes the read-only context clear, so an agent can tell when to call this rather than mutation siblings. It does not explicitly name alternatives or exclusions, but the resource and read intent are unmistakable.

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