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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered without the description. The description adds only that it fetches a single record by Id; it says nothing about not-found/error behavior or what a missing Id returns. Adequate against annotations but not rich.

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?

A single front-loaded sentence with the verb, resource, and key up front, followed by the usage qualifier. Efficient with no wasted clauses, though the trailing 'when no search or write answer already holds it' is slightly awkwardly phrased.

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 read-by-Id tool with full annotation coverage, the description is mostly sufficient. Since there is no output schema, it should ideally hint at what a tax code record contains or what happens on a bad Id; that gap keeps it at minimum-viable rather than complete.

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%, so both 'id' and 'company' are already documented in the schema. The description only echoes 'by Id' and adds no format, lookup, or company-selection nuance beyond the schema. Baseline 3 applies when the schema carries the load.

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+resource+key: 'Get a single tax code from QuickBooks Online by Id.' This clearly separates it from the list-style 'search_tax_codes' sibling by scope (single vs many). It stops short of explicitly naming that sibling, so the differentiation is implied rather than stated.

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 clause 'when no search or write answer already holds it' gestures at when to prefer this tool over search/write paths, which is real guidance. However it is vague about which alternatives exist and gives no explicit condition (e.g. 'use search_tax_codes to find an Id first'). Implied usage rather than explicit routing.

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