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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds a real behavioral trait beyond that — retrieval is semantic ('by meaning as well as keywords') — but says nothing about result ordering, whether older chats are truncated, or how the limit interacts with ranking.

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, front-loaded with the resource and scope, and the second sentence earns its place by eliminating a costly misidentification with other assistants' history. 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 two-parameter read-only search with full schema coverage, the definition is nearly complete. Without an output schema, a brief note on what a result contains (the matched message plus context, excerpt length) would close the last gap.

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%, with both query and limit documented in the schema itself, so the baseline is 3. The description contributes no additional detail on how the query is interpreted semantically or what the default of 5 means for ranking breadth.

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 names a specific verb (search) and resource (the user's past chats with the Achriom librarian) and bounds it by source. However it does not distinguish itself from the many search_* siblings (search, search_library, search_book_content, search_youtube) present in the toolset, leaving that ambiguity unresolved.

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 by the scope statement: it applies to Achriom librarian chat history, not Claude's or other assistants'. The negative scoping is genuinely useful, but no positive when-to-use condition or named alternative is given for the other search-family tools.

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