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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safe-read profile is covered by structured data. The description adds genuine non-annotation behavior: the matching rule (every word in q must appear in name, domain, summary, or category) and the meaning of agent_ready (llms.txt, official MCP registry entry, or public API). It does not describe result ordering, pagination behavior, or what happens at the caps, so the behavior layer is useful but not complete. That fits 3 against the annotation baseline.

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?

Four tight sentences: purpose first, matching semantics second, filters third, return shape and escalation to get_tool last. The parenthetical category list is dense but earns its place by showing scope. No filler or restatement of the title.

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 read-only search with five optional parameters and no output schema, the description covers purpose, matching, filters, and return shape ('brief records'), which is what an agent needs to call it correctly. The remaining gap is that limit/offset behavior and result ordering are never described. That is a minor incompleteness rather than a blocking omission.

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 40%, and the description compensates materially: it explains q as an AND-matching search across specific fields, defines agent_ready as a capability predicate, and anchors category to list_categories. Only limit and offset remain semantically undocumented beyond their numeric bounds. That is a clear net addition over the schema, not complete coverage.

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 (search) plus the resource (Fourth Feed directory of AI video tools) and enumerates the coverage areas: generators, avatars, editors, dubbing, lyric videos, faceless shorts, video APIs. It also distinguishes itself from get_tool by noting that this returns brief records only, so an agent can tell search from fetch without opening a 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?

The description gives concrete routing guidance: it points to list_categories for category ids and to get_tool when a full record is needed. It also defines the meaning of agent_ready so an agent knows when that filter is appropriate. It stops short of stating when not to use it (e.g., browsing new entries versus searching), so it's clear guidance rather than exhaustive when/when-not.

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