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

Annotations declare readOnlyHint=true and idempotentHint=false, so the safety profile is already covered. The description adds useful domain context by defining invariants and listing common examples, but it does not disclose return format, ordering, or whether the list is static or dynamic.

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?

The description is front-loaded with the core purpose and then adds definition and examples. It is appropriately sized for a simple zero-parameter list tool, though the definitional sentence is slightly more than strictly necessary for invocation.

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 simple read-only list endpoint with no parameters and no output schema, the description is largely complete: it says what is returned and gives example invariant names. It could still mention whether the list is exhaustive or whether it should be paired with get_invariant, but the annotations already cover the safety context.

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 and the schema has no properties, so there are no parameter semantics to document. Per the rubric, zero parameters gives a baseline of 4.

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: returns the list of available protocol invariants. It defines what invariants are and gives examples, making the output clear. However, it does not explicitly distinguish itself from the sibling get_invariant tool, which likely retrieves a single invariant.

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 phrase 'available protocol invariants that can be checked' implies this tool is used to discover invariant names, probably before calling get_invariant. But there is no explicit when-to-use guidance, no alternatives named, and no when-not-to-use condition.

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