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

The readOnlyHint annotation already signals a safe read operation, so the description does not need to restate that. It adds value by describing the return shape (sessions with titles, summaries, dates), but does not mention ordering, pagination beyond the limit parameter, or any other behavioral details beyond what the schema and annotation already provide.

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?

The description is compact and front-loaded with the tool's core purpose, followed by a clear 'use this when' statement and a brief returns section. It contains no filler, and the structure makes the main purpose immediately visible.

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?

Given that all parameters are optional and fully documented in the schema, the annotation declares read-only behavior, and the description includes a return-shape summary, the tool is adequately specified for an agent to select and invoke it correctly. The only minor gap is the lack of sibling differentiation, but this does not block correct use.

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?

The input schema already documents all four parameters thoroughly with descriptions, defaults, and formats, yielding 100% schema coverage. The description adds no extra parameter semantics beyond the high-level summary, so the baseline score of 3 is appropriate.

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 clearly states that the tool searches past chat sessions and returns session metadata, and pairs it with an explicit trigger ('when the user asks about previous conversations'). It is specific enough to be distinguished from search_emails or search_calendar, though it does not explicitly name any sibling alternative.

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 provides a concrete usage context: 'when the user asks about previous conversations, past discussions, or wants to find something they talked about before.' This gives clear when-to-use guidance, but it does not mention when not to use it or point to alternatives like search_linkedin_message_history or get_chat_messages.

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