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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so the trailing 'Read-only' adds nothing and is mildly redundant. The description does add real context by explaining what each selector means ('due' = review has come round, 'weak' = answered wrongly or forgotten). It says nothing about ordering, default limit, or what a returned word 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 compact sentences, front-loaded with what the tool returns and followed by the practice-session guidance. The closing 'Read-only' is the one wasted clause since annotations already carry that fact.

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 three-parameter read tool with no output schema, the description covers the selector semantics and usage flow but omits the limit parameter's behavior and any hint about result shape or ordering. Adequate to call correctly, not complete.

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 only 33%: 'language' is documented in the schema, 'limit' is documented nowhere, and 'need' is only an enum. The description compensates well for 'need' by defining all four values, but leaves 'limit' (1-50) entirely unexplained, so the gap is only partly closed.

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+resource: returns the caller's own vocabulary, filtered by a 'need' selector. The four selector values are named and glossed, which makes the tool's scope concrete. It does not distinguish itself from the sibling language_get_vocabulary, so an agent must infer the difference.

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?

Gives explicit sequencing guidance for the primary use case: 'ask for due first, then weak' when building a daily-practice session. It does not say when to prefer this over language_get_vocabulary or what to do outside a practice session, but the main context is clear.

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