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

Annotations declare readOnlyHint=false and destructiveHint=false, so the mutation and safety profile is already known. The description adds genuinely new behavior: names are unique per account, duplicate names are rejected rather than merged, and totals are reported in the portfolio currency while holdings remain in their listing currency. It stops short of describing failure modes or response shape.

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?

Three tight sentences, front-loaded with the core action and workflow next step. The closing currency sentence overlaps somewhat with the schema's own parameter description, so it is slightly less efficient than it could be, but nothing is 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?

With only two parameters, full schema coverage, and no output schema, the description supplies everything an agent needs to decide and call correctly: purpose, workflow handoff, confirmation requirement, and uniqueness constraint. Only the response/error behavior is left implicit.

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 100% and the schema already documents both name and currency, including the ISO-code list and default. The description's currency sentence largely restates the reporting semantics that the schema parameter description already carries, so the baseline 3 applies.

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 ('Create a new, empty portfolio') and scopes it to the user's own account, which cleanly separates it from siblings like GetMyPortfolio and DeleteMyPortfolio. It also names the follow-up tool AddPortfolioLot, so the agent understands its place in a workflow.

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?

Explicitly says what to do next ('add holdings to it with AddPortfolioLot') and adds an operational guardrail ('Ask the user before creating one, since it is their account'). That is a clear when-to-use plus a precondition, which is more than most definitions provide.

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