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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description still adds meaningful behavior: delays are recorded as their own events and never overwrite the original plan, coverage goes back to 2020, and the 'latest slice for all tiers; full history Pro (never a 403)' note discloses a real access-tier constraint.

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?

Well front-loaded: identity of the log first, then row shape, then USE/DO NOT USE, then filters. It is dense and longer than average, but nearly every clause carries actionable information; only the citation line is filler.

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 9 params at 0% schema coverage and no output schema, the description compensates well by enumerating returned row fields (foundry, fab_name, event_type, event_date, summary, source URL, verbatim quote, is_projection) and the lifecycle semantics. The one shortfall is the undocumented date-range filters, which leaves part of the parameter surface unaccounted for.

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 0%, so the description must carry the load. It documents 5 of 9 filters and usefully expands the event_type enum (announced|groundbreaking|topping_out|equipment_move_in|risk_production|hvm_start|expansion|delay|cancellation|conversion), which the schema lacks. However, the date-range parameters (from, to, since, all) go entirely unexplained, leaving a real gap.

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 resource and scope: the dated construction & ramp event log with its full lifecycle (announcement → groundbreaking → move-in → risk production → HVM), including expansions and schedule slips. An agent instantly knows this is the fab-milestone timeline tool and can distinguish it from capacity or allocation tools by name.

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?

Explicit USE THIS FOR block names concrete queries ('which fabs hit a milestone recently?', 'which projects have slipped?') and a DO NOT USE block routes to two named siblings (get_fab_capacity, get_foundry_allocation) with the condition that selects each. This is exactly the when/when-not/alternative guidance the dimension asks for.

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