decode_cnr_number

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

Annotations already declare readOnlyHint=true, openWorldHint=false, and idempotentHint=true, so the safety profile is covered. The description adds that it performs format validation alongside decoding, which is useful, but the trailing 'Not legal advice' disclaimer is boilerplate rather than behavioral disclosure. With annotations carrying the safety burden, a 3 is appropriate.

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 Args/Returns/Notes layout is front-loaded and easy to scan. The 'Not legal advice. Consult a qualified advocate.' sentence is filler that does not help an agent invoke the tool, and the Returns line is vague, but overall it is tight.

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 single-parameter, read-only decoder with an output schema, the description covers purpose, trigger, input constraint, and return shape. The output schema relieves it of explaining decoded fields, so nothing critical is missing, though the vague Returns line and boilerplate disclaimer keep it short of a 5.

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 schema's own description ('Spaces and hyphens are stripped automatically') is actually richer than the description's restatement of the 16-character constraint. The description adds no syntax or format detail beyond what the schema already provides, so baseline 3 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 states a specific verb+resource pair ('Decode and validate a 16-character CNR') and the tool is the only CNR decoder among the siblings, so it is implicitly distinguishable. It does not, however, explicitly contrast itself with adjacent decode/validate tools such as decode_state_code or validate_cin.

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 a clear usage trigger ('Use when extracting state, district, establishment, case type, year, and serial from a CNR number'), which tells the agent what problem this solves. There are no exclusions or named alternatives, but the context is unambiguous for a single-purpose decoder.

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