List news sources

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

Annotations already declare readOnly, idempotent, non-destructive, openWorld, so the safety profile is covered; the description adds value beyond that by enumerating the group vocabulary (news = Iranian general news, tech, sports) and disclosing that ids from here feed the `sources` filter on other tools. It stops short of covering result size or ordering, but nothing is contradicted.

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?

Front-loaded with the purpose, then the group vocabulary, then the next-step routing, in three short blocks with no filler. The backticked fragments and compressed phrasing ('Pass chosen ids as `sources` to nw_search / nw_latest_all to filter by group') make it slightly telegraphic rather than flowing, but nothing is wasted.

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 zero-param catalog tool with no output schema, this covers what is returned (groups and category slugs) and how to consume it downstream, which is the critical gap for param-less discovery tools. Minor residual ambiguity remains about the exact shape of an id versus a slug, but an agent has enough 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?

Zero parameters, so the baseline is 4. The description still earns its keep by explaining how this tool's output maps onto the `sources` parameter of nw_search/nw_latest_all, which the empty schema cannot convey.

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 and resource ('List the news sources') and immediately names the returned payload ('group and category slugs'). It also positions itself relative to siblings by declaring 'call this first' to obtain valid source/category values, so an agent can distinguish it from nw_search or nw_latest without opening a 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?

Gives explicit sequencing ('call this first'), names the concrete alternatives to use next (nw_latest, nw_search, nw_latest_all), and adds a disambiguation rule ('for technology questions use nw_tech_news'). This is exactly the when/when-not/alternative guidance the dimension asks for.

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