nvr_snapshot

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

With no annotations supplied, the description carries the full behavioral burden and does reasonably well: it declares read-only semantics, states the external prerequisites (RTSP + ffmpeg), clarifies the stream default, and previews the return payload. It stops short of covering failure behavior or where the export dir physically lives.

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 tight clauses with the core action front-loaded, then read-only/default, then prerequisites and output. No filler sentences; every fragment adds an actionable fact.

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?

An output schema exists, so the description needn't detail return values, yet it still summarizes path/bytes/sha256 helpfully. Combined with the read-only and prerequisite notes, it is nearly complete for a two-param tool, with only channel semantics left uncovered.

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 0%, so the description must compensate. It adds meaning for 'stream' (2=sub, beyond the bare schema default) but leaves 'channel' entirely unexplained—no indication of valid range, numbering, or how to discover it via nvr_list_channels.

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: 'Capture one JPEG frame from a channel's live stream into the export dir.' The 'one JPEG frame' phrasing cleanly separates it from siblings like nvr_sample_frames or nvr_contact_sheet that handle multiple frames, so an agent can route without opening schemas.

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?

Gives a real prerequisite ('Needs RTSP enabled and ffmpeg available') and notes read-only behavior, which is useful context for invocation. However, it never names an alternative tool or states when to prefer this over nvr_sample_frames/nvr_export_clip, so usage is only implied.

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