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

With no annotations, the description carries the full burden, and it does disclose meaningful behavioral facts: credential: none and cost: free, plus what the payload contains (rules text, publication status, content hash). It stops short of describing ordering or whether the hash is meant for integrity verification, which would have made it richer.

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?

Three short sentences with no padding, and the cost/credential facts are compact. The first-person preamble 'I want to understand the rules before using Peregrini' is intent framing rather than a purpose statement, which slightly delays a front-loaded read of what the tool returns.

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 zero-parameter read tool with no output schema, the description covers what an agent needs: what it returns, that it is the single authoritative source for the Rules of Court, that other instruments live elsewhere, and that there is no auth or cost. No material gap remains for invocation.

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?

This tool takes no parameters, so the schema is trivially complete and there is nothing for the description to disambiguate. Baseline 4 applies; no parameter guidance is needed or missing.

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 Rules of Court') and a specific output ('publication status and a hash of the exact bytes'), and it explicitly carves itself out from other instruments such as Practice Directions. However, it does not distinguish itself from the other rules-flavored siblings (house_rules_book, house_rules_index), so an agent still has to infer that boundary.

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?

It gives both a positive condition ('before using Peregrini' / wanting the Rules of Court) and a negative rule that routes agents elsewhere for other instruments, including Practice Directions. The alternative is expressed as a URL path rather than the sibling tool name (read_instruments/read_instrument), so the routing is slightly indirect but still actionable.

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