13F Portfolio Clone Backtest

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

Annotations only supply readOnlyHint=true, so the description carries most of the behavioral load and does so well: it discloses the reconstruction methodology, the filing-lag rebalancing, raw-price valuation, that a split without a certified price basis suppresses returns, and that the window is not silently shortened. These are non-obvious operational traits that meaningfully affect interpretation.

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?

Front-loads the purpose, then layers methodology, outputs, and the failure mode in three dense but coherent sentences. The split-price caveat is slightly tangential but earns its place by setting honest expectations; overall tight with little waste.

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?

With no output schema, the description compensates by enumerating the returned metrics (price return, CAGR, max drawdown, price-return alpha) and naming the conditions under which returns are unavailable. Nothing essential for correct invocation is missing.

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 the schema already documents defaults and the fromDate-overrides-windowYears precedence. The description's framing of 'either... windowYears or... fromDate/toDate range' adds only marginal interpretive value over that, so the baseline of 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 verb ('Backtest'), a specific resource (an institutional filer's reported 13F portfolio) and a comparison target (market benchmark). It is clearly distinguishable from siblings like GetInstitutionPortfolio or CompareInstitutionPortfolios, which report holdings rather than simulate performance.

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?

Explains the two operating modes clearly: a trailing window via windowYears or an anchored window via fromDate/toDate, which tells the agent when each parameter set applies. However it never names a sibling alternative or states an explicit when-not-to-use condition.

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