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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavioral context: results are a union across two collection mechanisms, so an agent must not assume a publisher missing from one channel is missing entirely. It still says nothing about ordering, pagination behavior, or what a source entry contains.

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 short sentences, front-loaded with the scope and followed by the one nuance that changes interpretation. No filler. It is arguably under-specified rather than verbose, and 'this record' is an unanchored reference.

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 4-parameter list tool with no output schema and no annotations gap on safety, the description covers the semantic core but leaves the two undocumented parameters and the shape of a returned 'source' unexplained. An agent can call it without arguments, but cannot use q or bucket confidently.

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?

Only limit and offset are documented in the schema (50% coverage); q and bucket have no description anywhere. The description does not mention any parameter, so an agent gets no hint about what q searches over or what values bucket accepts — exactly where compensation was needed.

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 resource (publishers/sources) and its scope: everything the record collects via feed OR sitemap. That is far more informative than the title 'List sources'. However, it never uses an explicit verb like 'list'/'returns' and refers to 'this record' even though the schema has no record parameter, leaving the implicit scoping slightly fuzzy.

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 second sentence implies when the union view matters ('A publisher absent from one may be present in the other'), so the tool's raison d'être is inferable. But there is no explicit when-to-use, no mention of when a filtered lookup would be better, and no guidance tying it to the sibling tools (fab_profile, find_fabs, etc.).

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