today_summary

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

With no annotations, the description carries the load and does well: it discloses a version prerequisite (app 3.8+), implies a pure read aggregation, and summarizes the returned sections in place of an output schema. It stops short of stating data-availability edge cases (e.g. what happens when there is no sleep or focus record yet), which is the one remaining behavioral gap.

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?

Two sentences, front-loaded with the scope enumeration and closing with the decisive routing instruction. The long middle list is dense information rather than padding, since it replaces a missing output schema.

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?

For a zero-parameter, no-output-schema aggregator, the description supplies everything needed: what is aggregated, the version requirement, and the routing rule against composing sibling calls. Nothing an agent needs in order to call it 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?

The tool takes no parameters, so there is nothing to disambiguate and the baseline applies. The description correctly does not waste words on inputs.

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 opens with a concrete noun phrase ('今天的一帧全景') and then enumerates exactly which aggregates it returns: todos, habit completion, water ml/goal, sleep minutes + streak, focus rounds/minutes, and latest countdown. This is clearly distinguishable from the single-domain siblings such as water_today, focus_today, and list_sleep.

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 states the trigger condition explicitly ('回答「今天怎么样」只需这一次调用') and the anti-pattern ('不要拿四张表拼'), which steers the agent away from fanning out to the sibling list tools. An agent knows both when to call it and when not to.

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