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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety and side-effect behavior need no restating. The description adds the accepted input shapes, but says nothing about what happens when a URL or slug does not resolve, which is the main behavioral unknown for a fetch-by-id tool. The presence of an output schema removes the need to describe return values.

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, both earning their place: the first gives the trigger, the second gives the input shape. The usage trigger is front-loaded and there is no filler.

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 full schema coverage, rich annotations and an output schema, the description covers the two things that matter: when to call it and what to pass. Only failure behavior on an unresolvable link is unaddressed, a minor gap given the otherwise complete picture.

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 single parameter's description already states 'A yani.study/phrases/… URL, or its last part.' The description's 'Takes the phrase's page URL or the last part of it' restates that in plainer language but adds no format, case-sensitivity, or validation detail beyond the schema. 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?

The description uses a specific verb ('show one phrase ... in full') on a specific resource, and the phrase 'from an earlier result' implicitly separates it from search_phrases. It stops short of naming the sibling outright, so the contrast is inferential rather than explicit.

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?

Two clear trigger conditions are given: the user shares a yani.study phrase link, or a phrase from a prior result needs to be displayed in full. There is no explicit 'do not use for searching' exclusion, but the 'earlier result' framing routes lookup-style requests to search_phrases.

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