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

The readOnlyHint annotation already indicates a safe read operation, so the description does not need to restate that. However, the description adds no additional behavioral context such as pagination, default time range (though that is in the schema), data granularity, or how the history is constructed. With annotations covering safety, the minimal description offers little extra transparency.

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 description is very short and free of fluff, which is good, but it is under-specified. It is a single phrase that does not elaborate on the nature of the returned data or any important nuances. It is concise but lacks the structure that would make it genuinely useful.

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?

Given the low complexity (one optional parameter, no output schema), the description is still incomplete. It does not describe the return format (e.g., array of {date, value}), the frequency of data points, or whether the current value is included. Since there is no output schema, the description should fill that gap, but it does not.

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 schema has 100% coverage for the single 'days' parameter, including default, min, max, and a clear description. The tool description adds nothing about the parameter, but the baseline of 3 is appropriate because the schema fully documents 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 the resource (portfolio value) and the time dimension (history over time), so the core purpose is discernible. However, it is vague about the exact output (e.g., a time series of values, frequency, currency) and does not differentiate from sibling tools like get_portfolio_analytics or get_total_portfolio_view. It is not a tautology, but it lacks specificity.

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?

No guidance is provided on when to use this tool versus the many related portfolio get_* tools. The description does not mention alternatives, exclusions, or typical use cases. An agent must infer usage solely from the name and generic description.

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