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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds valuable behavioral context: it returns a compact overview (peak + dip windows, current level, calibration state) rather than an hourly dump, defaults to today, and handles the no-sleep-data case with a nudge. It also explains the modeling nature of energy (modeled, not measured) for past days. This goes beyond annotations without contradicting them.

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?

Four sentences, each earning its place: purpose, differentiation, parameter behavior, return format, and edge-case handling. Front-loaded with the core purpose and use case. No fluff or repetition.

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?

Complete for a read-only single-parameter tool. The description covers what it returns, when to use it, prerequisites, and edge cases. The output schema is absent, but the description explicitly describes the return shape (peak + dip windows, current level, calibration state), so an agent knows what to expect. Nothing critical 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 description coverage is 100%, so the schema already documents the date parameter. The description adds context about defaulting to today and the meaning of future vs past days, which is useful but not strictly necessary given the schema's full coverage. Baseline 3 is appropriate.

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 ('Get'), resource ('forecast energy curve'), and purpose ('to schedule by their alertness'), and distinguishes itself from siblings by noting get_schedule and show_day don't include energy. The description clearly identifies what the tool does and how it differs from related tools.

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 when to use this tool ('when energy matters or the user asks about it'), names alternatives (get_schedule, show_day) and states they don't include energy. Also provides a prerequisite (at least one logged night of sleep) and behavior when unmet. This is comprehensive usage guidance.

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