render_chart

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

Without annotations, the description takes full responsibility for behavioral disclosure. It warns that relative paths resolve to the MCP server's cwd, not the bot's, and gives a Telegram-specific requirement. It doesn't mention file overwriting or permissions, but for a chart renderer this is adequate.

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: the first states the core functionality and output, the second adds practical path guidance. Both sentences carry necessary information with no redundancy, making it concise and well-structured.

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 7-parameter chart tool with no output schema, the description covers purpose, output format (PNG), file path constraints, and a specific use case (Telegram). Combined with complete schema descriptions, an agent has all needed information to invoke the tool correctly.

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 100% schema description coverage, the baseline is 3. The description references SMA, MACD, and volume panels, but the schema already explains all parameters in detail, so the description adds no unique semantic value beyond the schema.

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?

The description clearly states it draws a technical candlestick chart for one Vietnamese stock, listing components (SMA, MACD, volume) and output as PNG. This distinguishes it from sibling tools focused on data retrieval or analysis, making the purpose unambiguous.

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?

It provides context on when to use the tool (when a PNG chart is needed) and a specific condition for sending via Telegram. However, it doesn't explicitly compare with alternatives or state exclusions, so it falls short of the highest bar.

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