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 behavioral context by identifying the source as the 'public feed' and the 'general top-story stream' (i.e., unfiltered), which explains the absence of parameters. Pagination/limit behavior is not mentioned, but the output schema exists to cover return shape.

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?

Four short clauses with zero waste; the core behavior is front-loaded and the three routing hints follow. Every sentence earns its place.

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 no-argument feed tool with an output schema and read-only annotations, nothing an agent needs is missing: purpose, scoping, and the full sibling routing path to article/headlines/sections are all present.

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?

Zero parameters, so the baseline is 4. The description correctly frames the tool as taking no arguments by describing an unfiltered general stream, which is coherent with the empty schema.

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 (Fetch) and resource (RNZ top stories) and names the scope: the general top-story stream, not section-specific. It explicitly distinguishes itself from rnz_headlines, so an agent can route without opening schemas.

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?

Explicit routing: rnz_headlines for section-specific lists, rnz_sections to discover slugs, rnz_article with a returned URL for story bodies. When-to-use and alternatives are both spelled out.

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