plot_metric

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

Adds substantial traits beyond the annotations: 'Bounds clip already-fetched points, not a higher-resolution server query' clarifies the semantics of zooming, 'Also saves PNG locally without overwriting' explains the non-read-only side effect (consistent with readOnlyHint=false), and the untrusted-content warning flags prompt-injection risk. Session-marker provenance is also disclosed.

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?

Front-loaded with the core purpose followed by four dense, non-redundant sentences. Each sentence carries distinct information (scope, behavior nuance, side effect, security note) with no 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?

For a tool with no output schema, the description covers the return type, side effects, bounds semantics, and content-trust posture well. Remaining gaps are the undocumented non-zoom parameters, but the overall picture an agent needs to call and interpret it is largely present.

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?

With only 8% schema coverage across 12 parameters, the description must compensate. It meaningfully explains smoothing (EMA), axis bounds (x/y min/max as zoom), run_uids (up to 8), and session_markers, but leaves limit, stream, save_as, key, and axis format semantically thin.

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 action and output form ('Return a PNG plot directly to an image-capable agent') and names the scope ('Compare up to 8 runs'). This clearly distinguishes it from siblings like get_metric_series and get_history, which return data rather than a rendered image.

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 phrase 'directly to an image-capable agent' implies the usage context (agent that can consume images), and run count suggests comparison use. However, it never explicitly states when to prefer this over get_metric_series or compare_runs, nor any exclusions. Usage is implied rather than directed.

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