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

Annotations already mark this readOnly, idempotent, non-destructive, but the description adds substantial behavior beyond them: the full five-sleeve allocation rule, fund selection filters ($100M AUM, three years of prices, N-PORT filers), and the guarantee that every response carries the not_advice line in the not_advice field.

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?

The purpose and pre-call protocol are front-loaded, and nearly every clause carries operational weight. The middle construction-rule sentence is an unbroken run-on that is harder to parse than it needs to be, which costs structure points despite being information-dense.

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 5-parameter nested-object tool with no output schema, the description covers construction logic, parameter intent, the required pre-call questioning flow, refusal behavior, and the response's not_advice field. An agent has everything needed to call it and interpret the result.

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 only 40%, and the description compensates well by defining each band's stock-share range and pointing to etf_themes for themeIds. However, several schema facts (funds min/max, criterion default, feeCeiling bounds) are largely restated rather than extended, so it stops short of full semantic coverage.

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 and resource ('Builds a custom portfolio of US listed ETFs') and then spells out the exact construction rule, so an agent knows precisely what output to expect. It also routes the agent to sibling etf_themes for theme ids, distinguishing it from the search/screen/rankings tools.

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?

Explicit when-to-use guidance: gather missing choices in one short series before calling, never ask about personal financial/life attributes, never convert self-description into a band, and decline suitability/buy-sell questions. Alternatives and exclusions are both named rather than implied.

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