Expense Tracker MCP Server

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 mentions 'Update fields' which implies mutation, but doesn't specify permissions needed, whether changes are reversible, rate limits, or error handling. It lacks details on what happens if fields are omitted or set to null, and the output schema exists but isn't described. This is a significant gap for a mutation tool.

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 single, efficient sentence with no wasted words. It's front-loaded with the core action and resource, making it easy to parse quickly. Every part of the sentence contributes directly to understanding the tool's function.

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?

Given a mutation tool with 5 parameters, 0% schema coverage, no annotations, and an output schema (though not described), the description is incomplete. It doesn't explain behavioral aspects like side effects, error conditions, or parameter usage, and relies on the output schema for return values without context. For this complexity, more detail is needed to be fully helpful.

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%, so the description must compensate by explaining parameters. It only mentions 'ID' and 'fields' generically, without detailing the specific fields (amount, category, description, date) or their semantics (e.g., format for date, handling of null values). This leaves 5 parameters largely undocumented, failing to add meaningful context 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 the action ('Update fields') and resource ('an existing expense by ID'), making the purpose unambiguous. It distinguishes from siblings like 'add_expense' (create) and 'delete_expense' (remove), though it doesn't explicitly contrast with them. The verb+resource combination is specific but lacks detail on which fields can be updated.

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?

No guidance is provided on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., expense must exist), exclusions, or comparisons to siblings like 'add_expense' for creation or 'list_expenses' for viewing. The description only states what it does, not when it's appropriate.

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