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

Annotations already cover safety (readOnly, non-destructive, closed-world), so the bar is lower. The description adds real modeling context: constant yield and constant price growth assumptions, monthly reinvestment cadence, and the three return values. It does not disclose precision, edge-case behavior (zero yield, zero growth), or whether deposits themselves grow.

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 tight sentences: the first carries the mechanism and the optional input, the second carries the outputs. No filler, and the core purpose is front-loaded.

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?

There is no output schema, so naming the three returned values is a genuine completion. The reinvestment frequency and growth assumptions are stated, giving an agent enough to call it correctly. Minor gaps remain around whether deposits are flat or indexed and unit expectations (percent vs fraction) for yieldPct beyond the schema.

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 description coverage is 100%, so each parameter is already documented, including the 'yieldPct' alias note. The description confirms the default-0 nature of contributions ('optionally adding deposits') but adds no format, unit, or range detail beyond the schema. Baseline 3 applies.

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 mechanic: compounding a portfolio with a constant dividend yield and price growth, with monthly reinvestment and optional deposits. The resource (dividend reinvestment) and verb (compound) are unambiguous. It does not differentiate itself from siblings like compound_interest or savings_growth, which model similar accumulation.

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?

No guidance on when to choose this over compound_interest, savings_growth, cagr, or rule_of_72, all of which appear in the same sibling set and overlap conceptually. The phrase 'optionally adding deposits' hints at a use case but never states it as a selection condition.

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