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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely useful scope context: the exact count (57), that these are 'verified editorial' surfaces, and that media, puzzle, newsletter and partner surfaces are excluded — telling the agent what it will NOT get.

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 compact sentences, front-loaded with the resource and count, with the exclusion clause following. No filler and nothing an agent must scroll past.

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?

A no-param, read-only listing tool with an output schema, so return shape need not be explained. The description covers identity, scope, count, sibling relationship and exclusions — everything needed to call it 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?

The tool takes zero parameters, and the description correctly adds no parameter talk. Baseline for a no-param tool is 4; the enumeration scope described is the only 'input' semantics that could exist here.

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 (List) plus resource (the 57 verified editorial The National section slugs and canonical URLs) and explicitly ties them to national_headlines. An agent can distinguish this enumeration tool from its siblings without opening the schema.

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 phrase 'accepted by national_headlines' tells the agent this is the valid-input reference for that tool, which is a real usage cue. It stops short of an explicit 'call this before national_headlines when you need valid section values' instruction, so it is clear context rather than full when/when-not guidance.

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