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 value beyond that by disclosing what the response contains ('sync partner info and entitlement caps'), which is important since there is no output schema. It does not mention pagination or whether disconnected accounts are excluded.

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, zero filler. Scope is front-loaded in the first sentence and the usage cue in the second, which is exactly the right ordering.

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 no output schema, the description partially compensates by naming the return payload (partner info, entitlement caps) and the follow-up action. The one material gap is the unresolved overlap with the sibling 'list_calendars', which is not addressed.

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 document; the baseline for a no-param tool is 4. The description correctly avoids inventing filtering options that the schema does not support.

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 and resource ('List all calendars') and adds meaningful scope ('across all connected accounts'), so the agent knows this is a cross-account enumeration. However, it never distinguishes itself from the sibling 'list_calendars', which an agent could easily confuse it with given the near-identical names.

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 states the usage context: 'Use this before create_sync to discover which calendars are available.' That is a clear when-to-use cue tied to a named sibling tool. It stops short of an exclusion rule (e.g. how it differs from list_calendars).

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