get_thread_by_id

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

Annotations already declare readOnlyHint=true, so the description doesn't need to restate safety. However, it adds valuable context: the data comes from a 'local index' (implying cached or indexed state) and describes the return content in detail. This adds behavioral insight beyond the annotation.

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: first states the action and scope, second provides usage guidance. No fluff, front-loaded, every sentence serves a purpose.

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?

Despite lacking an output schema, the description fully explains what is returned (all messages, participants, labels, full metadata) and gives clear usage context. For a fetch tool with read-only annotations, this is complete.

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% (both parameters documented), so baseline is 3. The description adds subtle value by specifying that 'threadId' comes from 'get_threads' (source context) and that 'folders' can scope the search. This enriches the schema descriptions.

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 'Fetch the complete normalized thread record from the local index' with specific resource and scope, and distinguishes from sibling 'get_thread_brief' by noting the alternative returns a summarized view. This provides clear purpose and differentiation.

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?

Explicit guidance: 'Use when you need all messages in a thread. Prefer get_thread_brief for a summarized quick view that avoids returning the full message list.' This gives clear when-to-use and when-not-to-use, with a named alternative.

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