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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so 'Safe read-only operation' is largely redundant. However, the description adds genuine behavioral value by disclosing the return contents — subscription settings, polling health status, and unread count — which the agent cannot learn from any output schema since none exists.

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?

Three short sentences, front-loaded with the resource and payload, then the alternative routing. Minor waste in 'Safe read-only operation', which merely restates the supplied annotations.

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 description does the necessary work by enumerating what is returned and pointing to list_feeds. It lacks only edge-case detail such as behavior for an unknown or unsubscribed feed ID, which is minor given the tool's simplicity.

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% and the single feedId parameter is documented as the numeric feed ID with a positivity constraint. The description echoes that it is 'numeric' but adds no format, lookup, or resolution guidance beyond the schema, so 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?

States a specific verb ('Returns') and a precisely scoped resource ('a single subscribed feed by its numeric feed ID'), then enumerates the payload (metadata, subscription settings, polling health, unread count). It also names the sibling list_feeds as the broader alternative, so an agent can distinguish the two without inspecting schemas.

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?

Provides a clear selection rule: single feed inspection here, all subscribed feeds via list_feeds. It does not explicitly state when-not to use it (e.g., for discovering or searching feeds, which discover_feeds/search_items would cover), so the routing guidance is good but not exhaustive.

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