get_latest_image

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

With no annotations, the description carries the full burden. It discloses that it scans the last 200 messages, returns a downscaled photo along with the path to the full-resolution original, and provides an error sentence for unreachable group, expired session, or no photo. This gives agents a clear picture of behavior beyond the schema.

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?

The description is a bit long but each paragraph serves a purpose: primary action, usage guidance, and error handling. It is front-loaded with the main action and each sentence adds value, though it could be slightly more concise.

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 zero-parameter tool with no output schema and no annotations, the description covers the what, when, return value, and failure modes. It doesn't specify the exact success return format, but it mentions the image and path to the original, which is sufficient for an agent to use 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?

There are zero parameters, so the schema already covers everything. The description mentions a 'configured Telegram group' implying external context, but no parameter explanation is needed. The baseline for no parameters is 4, and the description doesn't introduce any confusion.

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 the tool's action: 'Return the most recent image posted in the configured Telegram group.' It uses a specific verb and resource, and implicitly distinguishes from the sibling wait_for_next_image by focusing on 'most recent' rather than awaiting new ones.

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 provides explicit when-to-use guidance: 'Use this when the user says they have just sent a screenshot.' It also explains the lookback window (last 200 messages) and advises cropping for fine print. It doesn't explicitly name the alternative tool, but the context implies when not to use it (waiting for a new image).

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