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

No annotations are provided, so the description carries the full disclosure burden. It hints at the return value ('signed head hash'), but says nothing about permissions, whether signing implies tamper-evidence guarantees, or any behavioral constraints of the call.

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 tight sentence with no filler and the key concept front-loaded. It is efficient, though the missing verb makes it read as a label rather than a complete statement of action.

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?

With no annotations and no output schema, the description must convey what the call yields; it does name the signed head hash, which is the core return datum. But it leaves the caller without any sense of format, when the ledger head is relevant, or how it relates to the sibling proof/checkpoint tools.

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 no parameter semantics for the description to compensate for. Baseline 4 applies.

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 resource — the signed head hash of the hash-chained audit ledger — which is more informative than a bare restatement. However, it is a noun phrase with no verb and no differentiation from siblings such as get_evidence_head or get_checkpoint, which likely return overlapping ledger-head material.

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, when-not-to-use, or alternative guidance. With five sibling retrieval tools (get_checkpoint, get_consistency_proof, get_evidence_head, get_inclusion_proof, get_usage), an agent is given nothing to choose between them.

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