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

Annotations only say it is a non-read-only, non-destructive mutation, which is thin for a write-ish operation. The description adds real behavioral context: it is recorded in history as a manual run, it returns HTTP 202 with state 'queued' or 'running', and it is idempotent while a sync is in flight. It does not mention permissions or failure modes, so it stops short of full transparency.

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?

Three short sentences, each carrying distinct information: purpose, side effect on history, and return/state behavior. Purpose is front-loaded and there is no 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 no output schema, the description usefully explains the response (202 plus state value) and the no-duplicate-start behavior. Given a zero-parameter, no-output-schema tool, this is nearly complete; only error/failure behavior is left implicit.

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 no inputs are required.

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 ('Starts a sync') and anchors it to a known UI action ('the same as Sync now in ContactZapp'), so the agent knows exactly what operation this is. No sibling tool in the list covers sync, so the operation is unambiguous within the toolset.

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?

The description implies a clear trigger condition (the agent wants a sync to run) and explicitly resolves the main alternative scenario: if a sync is already running, you get that one back instead of starting a second. There is no explicit when-not guidance or prerequisite statement, but the deduplication note covers the most likely ambiguity.

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