tester_present

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

With no annotations at all, the description carries the full disclosure burden, and the one real nugget it adds — that an automatic keep-alive already runs — is genuinely useful behavioral context. But it omits the core effect (that calling it refreshes the ECU's session/S3 timer and can prevent session timeout), whether the call is idempotent/safe, or what a positive vs. negative response means.

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 short sentences, zero waste, with the identifier first and the actionable caveat immediately after. Nothing is buried and nothing is padded.

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?

The output schema exists, so return values need not be explained, and the absence of parameters keeps the surface small. Still, for an agent-facing tool it lacks a plain-language statement of what the operation does and when invoking it actually matters, which is the remaining gap for a zero-arg mutation-style diagnostic call.

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; a baseline of 4 applies. The prose neither helps nor misleads on this dimension.

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?

It names the UDS service by its hex id and mnemonic ('0x3E TesterPresent'), which an agent with domain knowledge can map to 'keep the diagnostic session alive.' However, it never states in plain terms what the tool actually does — telling the ECU the tester is still connected — so an agent without UDS familiarity is left inferring the purpose from the name itself.

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?

'Rarely needed: a keep-alive already runs in the background' is an explicit when-not-to-use signal and points at the implicit alternative (rely on the automatic keep-alive). It stops short of stating the condition under which the tool IS the right call, e.g. when the background keep-alive has lapsed or a specific session requires an explicit ping.

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