Read Image

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It voluntarily states that it 'Does not rotate browser profiles; uses the same authenticated HTTP client as other tools,' which is valuable context about side effects (none) and auth. It also discloses the output format (base64 + mimeType). It does not discuss failure modes, but for a read-only fetch, 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?

The description is three sentences, front-loaded with purpose, and contains no filler. Each sentence provides distinct value: what it does, what it returns, and usage context. It is compact and to the point.

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?

There is no output schema, so the description appropriately explains the return value (MCP image content + text summary). It also covers the key context: when to use (after post/topic reads), what to pass, and the authentication behavior. It does not explain edge cases or error handling, but given the tool's simplicity and the schema's parameter details, it is sufficiently 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?

The schema already covers 100% of parameter descriptions, so the baseline is 3. The description adds minimal extra parameter semantics beyond restating the url formats and the 'and/or' relationship, which is already evident from the schema's optional fields. No new meaning is introduced beyond what the schema provides.

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 starts with 'Fetch Discourse post images for the model to view,' which uses a specific verb (fetch) and resource (Discourse post images), clearly distinguishing it from siblings like discourse_read_post or discourse_read_topic. It also specifies the return type (MCP image content), leaving no ambiguity about the tool's function.

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 clear context: 'Use after discourse_read_post/topic when raw contains .' This tells the agent exactly when to invoke this tool relative to sibling tools. It also explains how to use parameters ('Pass url ... and/or post_id'), though it does not explicitly state when not to use it or offer alternatives, so it falls short of a 5.

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