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

Annotations only declare readOnlyHint=true; the description adds genuinely useful behavior beyond that: the default time window (current year to date), the mutually exclusive input modes, the line items the report contains, and the underlying endpoint for traceability. It does not cover auth requirements or error/empty-period behavior, but for a simple read-only report this is solid disclosure.

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?

One dense sentence with the report contents and default front-loaded, followed by a short endpoint tag. Nothing is padded, though the raw 'GET /v2/...' reference is marginal value for an agent that only needs selection and invocation cues.

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 zero-required-parameter, read-only summary tool with no output schema, the description covers purpose, input modes, default behavior, and the shape of the returned figures. Missing only minor details such as error handling for invalid or future periods.

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, but the description adds real semantics the schema lacks: that from_date/to_date and accounting_period are alternative ways to specify the same window, and what the no-parameter default is. Only the non-mixing constraint is left implicit.

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 ('Profit and loss summary') and enumerates the report contents (income, expenses, operating and retained profit), so the agent knows exactly what data comes back. It is naturally distinct from the balance-sheet sibling, though it never explicitly contrasts itself with any sibling tool.

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 phrase 'for a date range or an accounting period' implies the two parameter modes are alternatives, and the default ('current year to date') tells the agent what happens with no arguments. However, there is no explicit when-to-use guidance, no exclusion (e.g. that accounting_period and dates should not be mixed), and no routing to alternative reports.

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