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 burden is lower; it adds the underlying REST mapping, which helps agents correlate with API docs. It does not disclose what happens on an unknown id (404 vs empty) or any auth/rate-limit behavior.

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, zero filler, with the core action front-loaded ahead of the endpoint reference. Every clause earns its place.

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 lookup with no output schema, the description never indicates what a reader object contains or how a missing id is reported, which are the remaining things an agent needs. Acceptable but thin given there is no output schema to fall back on.

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 100% and the sole parameter is documented as "The reader id (a Mongo-style hex string)," so the schema already carries the semantics. The description only restates "by id" and adds no format, validation, or sourcing guidance beyond it — baseline 3.

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 ("Fetch a single reader by id") and pins the exact endpoint (GET /reader/{id}.json). The word "single" implicitly separates it from knowledgeowl_list_readers, but that sibling is never named, so the differentiation is only inferable.

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: the required id parameter signals "call this when you already have a reader id," and by omission an agent would guess list_readers is the way to discover ids. There is no explicit when-to-use, when-not-to-use, or alternative routing statement.

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