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

Annotations already declare readOnly=true, idempotent=true, openWorld=false, destructive=false, so the safety profile is covered. The description adds genuine behavioral context beyond that: it discloses the shape of the returned research record and an important scope constraint (factual lookup only, no applicability determination), which sets correct expectations for the caller.

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 sentences, front-loaded with the verb, resource, and return contents, followed by the scope disclaimer. Every sentence carries distinct information — no restatement of the title, no filler.

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?

There is no output schema, so the description must describe the return value, and it does so thoroughly (the enumerated fields including Controls). Combined with the read-only annotations and the fully documented id parameter, an agent has everything needed to call this correctly.

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 100% and the single id parameter already documents the Magist id format, examples, and the pointer to search_regulations for discovery. The description only restates 'by its Magist id', adding no syntax or format detail beyond the schema, so the baseline 3 is appropriate.

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 ('Look up one regulation by its Magist id') with explicit singular scope, which separates it from the multi-item search_regulations sibling, and enumerates what the result contains (title, citation, jurisdiction, status, review dates, summary, Controls). An agent can tell exactly what this tool returns without opening the schema.

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 description draws a clear boundary: it 'returns facts about what a regulation says, not a determination of how it applies to a specific product,' and directs situation-specific questions to counsel. That implicitly routes the agent away from applicability work (compute_requirements) and toward find_counsel, though neither sibling is named explicitly.

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