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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial non-obvious behavior: the exact contents of each point, that `points` is empty when `dataSource` is "none", the reason (no imported costs, rate card or default rate), and the access/plan gate requirement. This is real behavioral disclosure beyond the structured fields.

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?

Return shape is front-loaded and every sentence carries information (division of labor, gating, empty-result rule). The final sentence is dense, with a nested parenthetical about pricing hours, but it is not 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 no output schema, the description fully covers what the agent needs: the point structure, the empty-result edge case and its cause, the access/plan prerequisite, and the sibling boundary. Nothing required to invoke or interpret the result is missing.

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 0% for the single `projectId` parameter, so the description carries the burden; it implies scoping to 'one project' but gives no id format or source. It also references `dataSource`, which is not an input parameter, which could momentarily confuse an agent about what it can pass.

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 ('EVM time-series for one project') and enumerates the returned series (date, PV, AC / S-curve). It explicitly demarcates itself from the closest sibling by saying CPI and estimates live in `calculate_evm`, so an agent can pick between them without opening a schema.

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?

It clearly assigns the CPI/estimate use case to `calculate_evm` and describes this tool as powering S-Curve and trajectory analyses, plus notes the shared access and plan gate. What it lacks is an explicit negative case or trigger phrasing (e.g. 'use this when you need the trend over snapshots, not a point-in-time index').

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