session_timeline

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

Annotations already declare readOnlyHint=true, destructiveHint=false and closed-world, so safety is covered. The description adds real value beyond that: it names the exact files read (captures/<file>.obcap, .openbaud/audit.jsonl), confirms no hardware is touched, and discloses the view:{kind:"timeline"} output contract plus the show_result rendering path.

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?

Three dense sentences, front-loaded with the core purpose, then inputs, then the output/rendering contract. Every sentence carries information, though the third sentence's phrasing is slightly convoluted.

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?

With no output schema present, the description usefully explains what the result declares (view.kind) and how it reaches the user via show_result, and it documents the two data sources. A mutation-heavy tool would need more, but for a read-only analysis tool this is close to 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 description coverage is 100%, so every parameter (path, from_ms, to_ms, buckets, max_inline_bytes) is already fully documented in the schema. The description mentions bucket folding and windowing only in passing and adds no syntax or format detail beyond the schema, so the 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: it lays a recorded capture out as a session timeline, combining rx/tx density buckets with audited operations as events. This is clearly distinguishable from sibling tools like session_stats or capture_frames, since it names both the input artifacts and the output shape.

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?

The description gives clear context for use: it operates on an existing capture file plus the audit log and explicitly notes 'no hardware', which tells the agent this is an offline analysis tool rather than a live one. It does not, however, explicitly name when to prefer session_stats or diagnose_frame over this.

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