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

Beyond the annotations (readOnlyHint=false, openWorldHint=true, non-idempotent), the description discloses that this creates a new session in the project, exercises a real network endpoint, and takes about five seconds, plus the required mcp:write scope. That is meaningful side-effect and auth context the agent would otherwise have to guess.

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 tight sentences that lead with the action, then the exclusion/alternative, then duration and scope requirement. No filler; every clause adds decision-relevant 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 one-parameter tool with no output schema, the definition covers purpose, cost (about five seconds), permissions, and side effects. The only gap is what the verification result looks like on success or failure, which matters slightly given there is no output schema.

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 coverage is 0% on the single project_id parameter, so the schema contributes nothing beyond a bare string type. The description implies scoping ('in the project', 'works for this project') which tells the agent what project_id selects, but gives no format or sourcing hints. Partial compensation only.

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 names a specific action — running a synthetic two-participant call (camera + microphone) through the real WebSocket endpoint into a new session — and explicitly contrasts it with the sibling verify_session for testing the app's own code. An agent can distinguish this from verify_session and create_session without opening a schema.

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 use case (prove the Synento side works for this project) and gives an explicit negative case with the correct alternative: 'it does not run or test the app's code — use verify_session for that.' Both the condition to use and the condition to route elsewhere are covered.

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