why_decision

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

No annotations provided, so description carries full burden. It discloses internal mechanics (tracing supersession chain with trigger/reason/evidence per hop) and output (active choice). However, it does not explicitly declare the tool as read-only or mention any side effects, auth needs, or rate limits. Basic transparency but lacks safety disclosure.

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, zero wasted words. Front-loaded with primary purpose, followed by clear usage examples. Efficient communication of key information.

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 the tool's moderate complexity and no output schema, the description adequately covers what the tool does and what it returns (traced chain with details, active choice). It provides usage examples. Minor gap: lacks details on return format or pagination, but overall sufficient for agent decision-making.

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% for both parameters. Description rephrases the query parameter as 'substring of the decision to explain', which adds little beyond the schema's description. Session_id is not elaborated. Baseline score of 3 is appropriate as description does not significantly enhance parameter understanding.

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?

Description clearly defines the tool as reasoning over decision history with specific verb 'reason' and resource 'decision history'. It explains the supersession chain tracing and active choice reporting, distinguishing it from sibling tools like analyze_file or checkpoint_session which serve different purposes.

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?

Provides explicit when-to-use guidance with example user queries ('why did we pick X', 'what happened to Y', 'what was the previous approach'). Does not mention alternatives or when not to use, but the context is clear and sufficient for an agent to select this tool appropriately.

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