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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds the behavioral trait that this returns a single tax rate (not a list), which goes slightly beyond the schema. However, it does not describe error behavior, authentication needs, or response format, but with annotations present this is acceptable.

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 a single, fluff-free sentence. The resource and operation are front-loaded, and it is appropriately sized for a simple getter tool. Every word adds some value.

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 simple get-by-id tool with readOnly annotations and fully described parameters, this is almost sufficient. However, it does not mention the optional company parameter's role in multi-company setups nor what the return value looks like (though no output schema exists). An agent can likely call it correctly, but some expectations (e.g., non-existence behavior) are unstated.

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% (both id and company are described), so the baseline is 3. The description only repeats the id's role ('by Id') and adds no meaning for the optional company parameter or any format details. It does not compensate for anything missing in the schema, but nothing is 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 states a specific verb ('Get'), a specific resource ('tax rate'), and a scope ('single... by Id'), making it clear this is a single-record retrieval. It distinguishes implicitly from the sibling search_tax_rates (search vs. single by Id) and from other tax-related getters (get_tax_code, get_tax_agency), though it does not name an alternative explicitly.

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 gives no guidance on when to use this tool versus alternatives like search_tax_rates. It only implies that the caller needs an Id, but does not state that this tool is appropriate when an Id is already known and a search tool should be used otherwise.

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