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

Annotations already declare readOnlyHint=true and idempotentHint=false, covering the safety profile. The description adds genuinely useful behavioral context: it explains that the tool returns a result showing whether the invariant is broken plus informative messages. That output disclosure is valuable, particularly since no output schema exists. It stops short of 5 because it does not discuss how results may vary across calls or any execution constraints.

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 three short sentences and is front-loaded with the core action. Each sentence contributes something, though the final usage sentence is fairly generic. It is appropriately sized for a simple one-parameter tool with no wasted exposition.

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 read-only, single-parameter tool with full schema coverage and existing annotations, the description covers purpose, output semantics, and a usage rationale. The absence of an output schema is mitigated by the description explaining what the result contains. It is nearly complete, with only minor nuance about non-idempotent behavior left to annotations.

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 description coverage is 100%, so the schema fully documents the single 'invariant' parameter, including example names. The description adds no additional syntax, format, or semantic detail beyond what the schema already provides. A baseline 3 is correct when the schema does all the heavy lifting.

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 states a specific verb and resource: 'Runs a specific protocol invariant check and returns the result.' This is clear and actionable, but it does not name or differentiate itself from the sibling list_invariants tool, which is the closest alternative. A 4 is appropriate for a clear purpose that lacks explicit sibling routing.

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 sentence 'Use this to verify protocol consistency and detect potential issues' provides an implied use case, but there is no guidance on when to prefer this over list_invariants or when it is inappropriate. This is the minimum viable level: a generic when-to-use statement without alternatives or exclusions.

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