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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so the safety profile is covered. The description adds genuine context: the return is Markdown plus structuredContent of shape {"result": <payload>} and the agent must branch on result.category ('descendants' | 'not_found'), plus a source/license note. Some of this overlaps the output schema, but the category-branching advice is actionable and not in the annotations.

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?

Purpose and the key routing constraint are front-loaded in the first two sentences, and the trailing sentences carry real payload-shape and licensing information. Sentences are dense and long, but each clause earns its place; 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?

With an output schema present, the description need not explain return values, yet it goes further by naming the result.category discriminant the caller must switch on. Parameter, safety, routing, and licensing concerns are all covered, leaving no gap for an agent.

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 both parameters are already documented in detail, including the leading-asterisk tolerance and part-of-speech examples. The description only restates the composite 'descendant handle (entry_id + word_class)' concept, so baseline 3 is appropriate — no meaningful meaning is added beyond the schema.

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 states a specific verb ('Fetch the full descendants payload') and resource (etymology, glosses, reflex tree for a lemma identified by a descendant handle). It explicitly distinguishes itself from the sibling scythian_search by noting that a default search already returns payloads inline, so an agent can route correctly without opening either schema.

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?

It gives an explicit when-to-use ('only when a search ran without inline payloads or left a match un-expanded') and a when-not ('a default search already returns each match's payload inline'). This is unambiguous routing guidance tied to the sibling tool's behavior.

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