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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the write/safe-mutation profile is covered. The description adds the useful constraint that CstIbsCbs is mandatory under the tax reform, but says nothing about permissions, validation failure modes, or uniqueness of a rule. Note the claimed obligation sits oddly with the schema, where CstIbsCbs is nullable and not in the required list.

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 compact sentences with the purpose front-loaded and zero padding. It is efficient, though the payoff per sentence is limited given how much parameter detail is omitted.

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 23-parameter mutation tool with 0% schema description coverage, the description covers only one enum and one mandatory-field note. An output schema exists, so return values need not be explained, but the input contract is far too thin for an agent to populate the tax fields 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 description coverage is 0% across 23 parameters, so the schema carries essentially no meaning and the description must compensate. It only explains the Tipo enum (1=NFe, 2=NFCe, 3=Energia/Comunicacao) and flags CstIbsCbs as required, leaving roughly 20 tax fields (CstIcms, AliqCbs, AutoAliq, EnquadramentoIpi, etc.) completely unexplained.

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 ('Cadastra uma nova regra de tributacao') and scopes the entity (CFOP + CSTs + aliquotas). It is clearly distinguishable from tributacao_consultar, though it never explicitly contrasts itself with tributacao_editar, the closest sibling.

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?

No guidance on when to create a rule versus editing one with tributacao_editar, nor any prerequisite or context condition. Usage is only implied by the verb 'Cadastra'.

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