Compute XIRR from a CAS

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

With no annotations, the description carries the burden of behavioral disclosure. It explains the cash-flow sign conventions ('Purchases and levies count as outflows, redemptions and dividend payouts as inflows') and how the series is closed by current value, which are meaningful behavioral details. It does not mention failure modes or whether the operation has side effects, but this is clearly a read/compute operation.

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?

Three tightly written sentences front-load the core purpose, use the sibling reference to add context, and finish with the essential cash-flow conventions. There is no filler; 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?

The description is complete enough for an agent to understand what the tool does, how flows are counted, and how it differs from compute_xirr. Gaps remain: the password parameter is unexplained, and without an output schema the return format is only implied ('annualised return').

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 75% and the schema already documents filePath, scope, and valueAt well, so the description does not need to repeat them. The description adds no new parameter detail, and the password parameter remains completely undocumented in both the schema and the description.

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 opens with a specific verb and resource: 'Compute annualised return (XIRR) from the real, dated cash flows in a consolidated account statement.' It also explicitly contrasts itself with compute_xirr, saying that tool handles arithmetic but this one pulls the flows from the statement, so an agent can tell them apart.

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?

It clearly implies when to choose this tool: when you have a CAS PDF with many dated flows, because 'nobody can hand-type years of SIP instalments.' It references compute_xirr as the alternative, though it stops short of explicitly stating 'use compute_xirr only when you have a small set of manually entered cash flows.'

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