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

Annotations already establish the safe read-only, idempotent, closed-world profile, so the bar is lower. The description adds real context beyond them: licensed sources carry a `licensed` object with provider, licence type and price, and it points to the endpoint that defines licensable publishers and the per-article cap.

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 sentences, front-loaded with the core action before the licence aside. The second sentence is information-dense but every clause earns its place by explaining the `licensed` field and the licensing endpoint.

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?

With no output schema, the description partially compensates by describing the `licensed` sub-field. However, it says nothing about pagination or what the overall result set looks like despite a `limit` parameter, leaving a meaningful gap for a list tool.

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%, so both `limit` and `domain` are fully documented in the schema. The description only restates domain filtering ('optionally by domain') and adds no syntax or semantics beyond what the schema already provides; 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?

Specific verb ('List') plus resource ('fetched sources') with a scope modifier ('optionally by domain'). It is clearly distinguished from sibling fetch_url (which acquires) and check_source (which inspects one), though it never names those siblings explicitly.

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?

Usage is only implied: 'optionally by domain' hints at the filtering case, but there is no guidance on when to use this versus check_source or scholar_search, and no listed prerequisites.

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