thread_merge_history

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

Annotations already declare read-only, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavioral context: the limit is scoped per original thread, all source and resume information is retained, and no remote issues are touched. It stops short of describing error or empty-result behavior.

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?

Short and front-loaded — the core read operation leads, and scoping caveats follow. It could be trimmed slightly since the per-thread limit point duplicates the schema, but there is no padding or 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?

A simple two-parameter read tool with a full output schema and complete annotations needs little more than this. The description covers what is returned, the per-thread limit semantics, and the non-mutating scope. Only edge-case behavior for non-merged or unknown thread IDs is unaddressed.

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%, so the schema already documents both parameters, including that limit is per original thread. The description's 'Limit applies per original thread' largely restates the schema field description, adding little meaning beyond it. Baseline 3 applies.

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 and resource: 'Read retained merged threads, progress notes and events with original IDs.' An agent can tell this is a history-retrieval tool, distinct from mutation siblings like request_thread_merge. It does not name a sibling alternative, so it stops short of a 5.

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 implied rather than stated: the tool applies after a merge, since it reads 'retained' merge sources. The negative guidance 'this does not fetch or change remote issues' excludes one class of expectation, but there is no explicit when-to-use versus list_open_threads or search_work, and no statement about what happens for an unmerged thread.

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