get_test_fixture

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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds important behavior: the tool returns a static fixture, does not consume quota, and test-mode keys yield deterministic canned results. These details go beyond annotations and help the agent understand the tool's side-effect-free nature.

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 two sentences, with the core purpose stated upfront. Every clause provides relevant information: endpoint, content, purpose, quota savings, and test-mode behavior. No fluff or redundancy.

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 parameterless tool with an output schema and comprehensive annotations, the description covers all needed context: what it returns, why to use it, and how test-mode affects results. There are no gaps in understanding when or how to invoke it.

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 tool has zero parameters, and the schema reflects this with an empty properties object. The description need not explain parameters. Since there are no params, the baseline of 4 is appropriate; the description doesn't need to compensate for any missing parameter info.

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 'Get the stable test fixture (GET /v1/test-fixture)' with a specific verb and resource, and enumerates the exact contents: 'a video URL + prompt + expected answer'. It distinguishes itself from sibling tools by focusing on testing/verification use case, making it unmistakable.

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 explains when to use this tool: 'for verifying an integration end-to-end without burning quota', and adds a conditional about test-mode keys. It implies this is for testing scenarios, but does not explicitly mention alternatives or when not to use it. Since siblings are unrelated, this is clear enough.

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