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

Annotations already establish readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds real value by disclosing the shape of the returned state (elapsed time, target end time, active template) and the non-obvious inclusion of enabled templates, which the agent would otherwise not know is bundled in — particularly useful since there is no output schema.

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?

A single front-loaded sentence with the verb and resource first, followed by a compact enumeration of returned fields. No preamble, no redundancy, nothing that could be cut without losing information.

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-argument read tool whose annotations fully cover the safety profile and which has no output schema, the description carries the entire burden of describing the return payload — and it does so field by field. The one remaining gap is routing: it never states when to prefer still_get_fasting_summary or still_get_fasting_history instead.

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 zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The description correctly implies the implicit scoping ("signed-in user's" state) rather than exposing a user identifier, which confirms no argument is needed.

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?

Names a specific verb and resource ("Get the signed-in user's current Still fasting state") and enumerates exactly what that state contains: fasting flag, start time, elapsed time, active template, target end time, and enabled templates. The word "current" implicitly separates it from still_get_fasting_history and still_get_fasting_summary, but no sibling is ever named explicitly.

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?

There is no explicit when-to-use guidance, no exclusions, and no named alternatives. Usage is only implied by the word "current," which a careful agent can map against the history/summary/list_templates siblings, but that inference is left entirely to the reader.

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