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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description goes well beyond them: it discloses the degradation modes (SEC-filing ETFs with no return/risk figures, leveraged/inverse/trust/multi-asset cases compared by weekly returns alone, with reason). This is unusually rich behavioral context.

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-loaded with the trigger condition and outcome list, and every clause carries information. It is dense and long, but the exhaustive edge-case enumeration largely earns its space rather than padding.

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?

An output schema exists, yet the description still specifies the shape of returns and the many reduced-output edge cases, plus holdings dates. Combined with annotation and schema coverage, an agent has everything needed to call and interpret it correctly.

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% with per-parameter descriptions and examples, so baseline is 3; the description adds value by constraining both parameters to US ETF tickers and requiring exactly two, which the schema does not state.

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 (compare) and resource (two US ETFs) and enumerates the exact questions it answers: overlap, duplication, cost/risk difference. It clearly distinguishes itself from siblings like get_etf_overlap_matrix and get_etf_holdings by naming them or their domain.

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?

Opens with an explicit trigger ('when the user names exactly two US ETFs') and closes with an explicit exclusion plus the alternative ('Not for three or more ETFs (get_etf_overlap_matrix)'). The when/when-not/alternative triad is fully covered.

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