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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds real behavioral context beyond that: results are ordered newest first, results are paged (cursor-based), and a paid plan is required. These are non-obvious traits worth the credit.

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 tight sentences with the capability front-loaded and the constraint second. Every clause carries information (facets, ordering, filtering, paging, plan). Not padded, though it is terse enough that some structure is lost.

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 12-parameter read-only search with full schema coverage and no output schema, the description covers what results look like (fields), ordering, paging, and the account-level prerequisite. An agent can call it correctly. Only the absence of explicit sibling routing keeps it from a 5.

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% across all 12 parameters, so the schema already documents date bounds, enums, limits and cursor semantics. The description only reinforces which facets exist (topic, tickers, sector, sentiment) and that paging occurs, adding little syntax or format detail beyond the schema. Baseline 3 applies.

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 ('Search Headlines API') and enumerates the result facets (topic, tickers, sector, sentiment score), which lets an agent distinguish it from get_headlines_sample and headline_event_card. It does not explicitly name the sibling it is not, so it stops short of a 5.

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 prerequisite ('needs a paid NEXUS plan on the linked account') is genuinely useful routing information. However, there is no guidance on when to prefer this over get_headlines_sample or get_headlines_api_info, so usage is only implied.

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