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

readOnlyHint=true already tells the agent this is a safe, non-mutating read, so the description's main added value is the field inventory it returns (publisher, endpoint, update rate, check status, notes). It says nothing about behavior for a missing id, error responses, or whether the result includes related records — gaps that matter less given the read-only annotation.

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 with the resource and selector stated first, followed by a compact field list. The enumerated fields are dense but earn their place because there is no output schema to describe the return payload.

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 one-parameter read tool with no output schema, the field enumeration effectively substitutes for return-value documentation, and the readOnly annotation covers the safety profile. The remaining omission is failure behavior for an unknown id, which is minor at this complexity level.

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 coverage is 0% for the single `id` parameter, so the description must carry the meaning — and "one source by id" does establish that the integer identifies a source record. It does not say where such an id comes from (e.g., a prior search_library result) or whether it is a catalogue id versus a publisher id, which leaves some ambiguity for a 0%-coverage parameter.

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?

The description names a specific verb and resource ("Full details of one source by id") and enumerates exactly what is returned, so an agent knows this is a single-record lookup rather than a search. It does not explicitly distinguish itself from siblings such as get_store or search_library, leaving that inference to the agent.

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 only usage signal is the implicit "by id", meaning the caller must already have a source identifier. There is no statement of when to prefer this over search_library or list_gaps, and no note about what to do when the id is unknown or invalid.

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