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

With readOnlyHint, idempotentHint, non-destructive and closed-world already supplied by annotations, the description still adds real value: it declares the consent and API-allowance gates and enumerates the side effects it explicitly does not perform (no saving, no order placement, no broker sync). It does not describe response shape, rate limiting, or what happens when the 50-holding cap is exceeded, so it is not fully transparent.

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?

Four compact sentences with the operation and its input contract front-loaded, followed by prerequisites, then exclusions, then the sibling pointer. Every sentence carries information; the only mild redundancy is the closing clause about accepting the existing stock-holdings contract, which restates the opening.

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 five-parameter tool with a nested holdings array and no output schema, the description covers preconditions and side-effect boundaries but never indicates what the analysis returns or how limit/offset/path affect results. The undocumented benchmark parameter is the largest gap, since its intent (comparison index) is not obvious from the schema alone.

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 only 20% (only 'path' is documented), so the description carries most of the burden. It explains the holdings contract well (symbol, shares, optional cost basis, max 50 items) but says nothing about benchmark, limit, or offset, leaving three of five parameters to inference. That partially compensates for the coverage gap but does not close it.

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 states a specific verb and resource ('Run the existing Portfolio API for up to 50 supplied stock holdings with shares and optional per-share cost basis'), which tells an agent exactly what is analyzed and the shape of the input. It also distinguishes itself from the sibling read_portfolio by noting that saved option holdings are read there, not here. Naming the operation as an API passthrough is slightly indirect but not confusing.

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?

Prerequisites are explicit ('Requires portfolio consent and existing service access/API allowance'), and the exclusions are spelled out: it does not save a portfolio, place orders, or synchronize a broker, and read_portfolio is the alternative for saved option holdings. What's missing is a positive when-to-use statement for ad-hoc supplied holdings versus analyzing saved data, though it is strongly implied.

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