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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered structurally. The description adds the default 'newest-first' ordering and worldwide source scope, but says nothing about result-set size behavior, pagination, or rate limits — modest value beyond annotations.

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?

A single front-loaded sentence that leads with ordering and resource, then enumerates filters. No filler, no restatement of the title, and nothing that could be cut.

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 21-parameter, open-world search tool with no output schema, the description plus rich schema covers the mechanics, and annotations cover safety. What is missing is any statement of result-shaping behavior (return format selection is only in the schema) or guidance on chaining with find_entities/list_sources, so the definition is workable but thin for the tool's complexity.

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 90%, so nearly every parameter is already documented in the schema (including the important semantic/keyword matching notes and format trade-offs). The description only re-lists the filter names and adds no syntax or interaction detail beyond what the schema provides, making the baseline 3 correct.

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?

Names a clear resource (news/headlines) and enumerates the filterable dimensions (words, language, country, topic, source, kind, time), so the agent knows this is the broad search/retrieval entry point. It does not name or contrast itself against siblings like list_stories or get_news_item, so it stops short of full differentiation.

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?

Implied usage only: the word 'optionally filtered' tells the agent filters are add-ons to a general query, but there is no explicit when-to-use-this-instead-of guidance versus list_stories, get_story, or find_entities, and no note about paging via 'before'/next links. Adequate but leaves routing to inference.

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