Record an official MCP metric snapshot

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

The description adds the 'never estimates' policy and official MCP source constraint, but fails to disclose side effects like whether the operation overwrites existing snapshots, creates duplicates, or fails if the post doesn't exist. With all annotation hints false, the description carries the transparency burden and does not meet it.

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 short sentences convey the core action, source, and a critical constraint. No repetition of schema details, tightly front-loaded, and every word earns its place.

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 write tool with 16 parameters, no output schema, and no nested objects, this description is too minimal. It omits identifier semantics, null-vs-zero handling, return value, and error behavior, leaving significant gaps for an agent deciding when and 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?

Schema description coverage is 0%, and the description does not compensate. It barely hints at capturedAt via 'timestamped' and identifier via 'against an existing post', but ignores the 15 other parameters, the required identifier, and ambiguity around nullable fields like estimatedValue given the 'never estimates' rule.

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 action ('Store timestamped metrics') and the target ('against an existing post'), with a specific source ('Substack's official MCP'). It is immediately distinguishable from sibling read/list tools and draft-writing tools.

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?

Provides clear context: use this only for metrics obtained from Substack's official MCP, and explicitly forbids entering estimates. It does not name alternative tools (e.g., get_post_performance) or mention when not to use it, but the source and the 'never estimates' rule give strong direction.

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