malformed_message

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

With no annotations, the description carries the full behavioral burden. "Deterministic" is a useful signal, but it never states whether the malformed frame corrupts or terminates the session, whether subsequent calls are affected, or how the client is expected to observe the violation. For a fault-injection tool, those side-effect semantics are the key information.

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 no filler. It is efficient, though the brevity is partly under-specification rather than disciplined conciseness.

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 fault-injection tool with no annotations, no output schema, and an undocumented enum, the definition is too thin: it omits what the response looks like, the side effects on session state, and how each variant maps to a violated rule. An agent can invoke it but cannot predict the consequences.

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% and there is one required enum parameter, so the description should have compensated. It does not list or explain the variant values, though "selected JSON-RPC rule" gestures at the enum and the values (missing-jsonrpc, invalid-jsonrpc-version, result-with-error) are largely self-describing.

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 concrete verb and output ("Return one deterministic response") and a concrete domain constraint ("violates a selected JSON-RPC rule"), which is enough to distinguish it from fault-injection siblings like duplicate_response or disconnect. It does not explicitly name those siblings, but the purpose is unambiguous.

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 when-to-use guidance, no statement of prerequisites, and no routing to alternatives. An agent must infer that this belongs in protocol-conformance testing and that siblings cover the other fault classes.

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