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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), so the description is not needed for that. It adds genuine context instead: the provenance of the numbers, the fact that they are beyond training data, the taxable-income-after-deduction semantics, and that comparison output includes threshold deltas between years. It does not describe response shape or ordering, but the added behavioral context clearly exceeds what annotations supply.

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?

Purpose and scope are front-loaded in the first clause, followed by content detail and then a caveat about training data. Every sentence carries information relevant to invoking the tool. It is dense but not padded; a slightly cleaner separation of return contents from the deduction caveat would improve it.

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?

With no output schema, the description must convey return contents, and it does: brackets, rates, per-filing-status thresholds, tax at bracket floors, and year-over-year deltas. For a read-only, zero-required-parameter lookup tool this is nearly sufficient. The one unresolved gap is the qualifying_surviving_spouse enumeration value, which the prose folds into 'four individual statuses' without explaining the discrepancy.

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%, so the schema already defines all three parameters, including enums and defaults, making 3 the baseline. The description adds a small amount beyond that: it clarifies that 'compare' yields the change in each threshold versus the other year, which is more concrete than the schema's 'Include the other year for comparison.' It does not address the mismatch between the enum's qualifying_surviving_spouse value and the phrase 'four individual statuses.'

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 resource (federal income tax rate schedule for tax year 2027/2026), its source (IRS Rev. Proc. 2026-35), and the exact content returned (seven brackets, tax at bracket floor, threshold deltas per filing status). That is far more than a restatement of the name. It stops short of naming how it differs from siblings like get_tax_amounts, which also appears to surface per-bracket figures, so the boundary is left implicit.

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?

There is implied guidance: 'A model cannot know the 2027 numbers from training' signals this tool is the authoritative source for current-year thresholds, and 'Thresholds apply to taxable income after the deduction' tells the agent to pair it with a deduction step. However, no alternative is named and no when-not condition is given, so the agent must infer that calculate_federal_income_tax handles the actual liability computation rather than this tool.

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