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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: totals are in the user's currency, and holdings without a live price are valued at cost with null P/L. This goes beyond what annotations provide and clarifies edge-case output behavior.

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?

Two sentences with zero filler. The first sentence delivers the core action and output fields; the second adds a specific, valuable clarification about currency and valuation. The description is front-loaded and every sentence earns its place.

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 no-parameter read-only list tool, the description covers the essential output semantics: what is listed, the fields included, and the edge case for unvalued holdings. It doesn't specify pagination or exact output structure, but those are likely unnecessary given the simplicity. The description is complete enough for an agent to call 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?

The tool has zero parameters, so there is nothing for the description to add beyond what the schema implies (an empty object). The baseline for 0 params is 4, and the description doesn't attempt to introduce nonexistent parameters. No further elaboration is needed.

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 ('List'), a specific resource ('portfolio holdings'), and the key data fields returned (market value, P/L, allocation). It clearly distinguishes from sibling list tools like list_accounts or list_books by focusing on holdings. The purpose is unambiguous.

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?

Usage is implied: if an agent needs to see portfolio holdings, this is the tool. However, there is no explicit guidance on when to use it versus alternatives, no exclusions, and no mention of related tools like list_accounts. The context is clear but not fully explicit.

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