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

Annotations already declare this a non-destructive, closed-world read, so the safety profile is covered. The description adds useful scope detail by breaking out what the carrying-cost calculation includes (manager fee plus custodian margin and short rebate spreads), but with no output schema it says nothing about the shape of results — whether it returns a ranked recommendation, a year-by-year cost table, or illustrative-only figures — nor what tax assumptions underlie the comparison.

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-loading with 'Use this tool whenever' is a good structural choice, but the body is a single dense run-on sentence that packs strategy names, four extension ratios, cost components, three vendor names, and two custodians into one clause chain. It is efficient in length but costly to parse, and the extension ratios are effectively restated from the enum.

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 7-parameter read-only comparison tool with no output schema, the description covers the TALS side thoroughly and flags the 2026 data vintage, which is important for an agent reasoning about currency of results. However, the two comparison arms named in the title — direct indexing and a staged ETF sale, the latter driven by the stagedYears parameter — never appear in the description body, and no tax-rate assumptions are stated, leaving the agent unsure what the comparison actually benchmarks against.

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; the description climbs above it by tying extensionPct values to real-world products (AQR, Cache, Brooklyn, Neuberger Berman SMAs) and by pairing custodian choice with actual 2026 Schwab/Fidelity minimums and restrictions. It still leaves marginType ('portfolio' vs 'reg_t') effects on short rebate and margin cost unexplained, a moderate residual gap.

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 names a concrete analysis (diversifying a concentrated low-basis stock position) and enumerates the specific strategies and sub-tasks involved: TALS extension variants (130/30 through 300/200), carrying-cost computation (manager fee, custodian margin, short rebate spreads), and 2026 Schwab/Fidelity account minimums. An agent can distinguish this from the sibling SBLOC, Roth, RMD, and estate tools without opening the schema.

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 'use this tool whenever...' framing gives explicit positive triggers tied to user phrasing (advisor asks how to diversify a concentrated low-basis position, evaluates a 130/30 or 200/100 SMA, checks custodian minimums). It stops short of naming exclusions or sibling alternatives — most notably it never says to use compare_sbloc_borrow_vs_sell instead when the client's question is borrowing against the position rather than exiting it.

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