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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, and the description reinforces this with "Does not change or save the plan" — meaningful because the tool accepts mutation-shaped inputs (extra_days, new durations). It also enumerates output content (baseline and per-scenario end dates, working vs calendar day delay, new critical path, tasks entering/leaving criticality, float absorption), which is partly redundant with the output schema but still adds framing.

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?

Front-loaded with the use case and examples, then inputs, then outputs, then the exclusion. It is somewhat long and the return-value enumeration partly duplicates the output schema, which costs it the top score, but every sentence is on-topic.

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 an output schema present, the description need not explain returns — yet it still does, plus it states the read-only contract, the parameter relationship to the sibling planner, and the routing rule. Nothing an agent needs to select and invoke this correctly 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 100% with detailed nested descriptions, so the baseline is 3. The description adds genuine semantic framing beyond the schema: tasks/calendar mirror plan_project_timeline, and each scenario's changes are one of three mutually exclusive shapes (extra_days, a new duration, or a new start-no-earlier-than date) — clarifying how the nested change object is intended to be used.

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+resource (compares timeline what-if scenarios against a baseline) and backs it with two concrete user-utterance examples ("if Design slips 5 days, when do we finish?"). It also explicitly contrasts itself with the sibling plan_project_timeline, so an agent can route without opening either 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?

Gives an explicit trigger condition (task slips, takes longer/shorter, starts later; critical-path questions) and an explicit exclusion with the alternative named: "Do not use for the first schedule of a project (use plan_project_timeline)." That is both when-to-use and when-not-to-use.

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