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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower; the description still adds real context by naming the data source (official College Board distributions) and flagging that two of the four ranking metrics are only available for 2024 and 2025. It stops short of saying what happens if mean/test_takers is requested for 2026 or what the returned rows contain.

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?

Two sentences, front-loaded with the ranking operation and its metrics, then the invocation rule. The dense parenthetical about metric availability is slightly awkward and would read better as its own clause, but there is no filler.

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 5-param, all-optional ranking tool with no output schema, the description covers metrics, data source, defaults implied by schema, and the exam-list-vs-all behavior. Minor gaps remain: the row shape returned and handling of unrecognized exam names 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 coverage is 100%, so the baseline is 3, but the description adds meaning the schema lacks: it defines pass_rate as 'share scoring 3 or higher', explains the exams list purpose, and discloses the 2024/2025-only restriction on mean and test_takers, which is absent from the sort_by enum description.

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 (ranks) and resource (AP exams for one year) plus the exact ranking keys: pass rate, share of 5s, mean score, test takers. This is clearly a cross-exam ranking operation, distinguishable from siblings like get_ap_score_distribution (single exam distribution) and list_ap_exams (enumeration only).

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?

"Give a list of exams to compare a few, or leave it empty to rank all of them" gives explicit invocation guidance for the main parameter, plus a data-availability caveat (mean and test takers only for 2024/2025). It does not, however, name when to prefer a sibling tool such as get_ap_score_distribution for a single exam.

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