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ispyridis

Calibre MCP Server

by ispyridis
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Server Quality Checklist

58%
Profile completionA complete profile improves this server's visibility in search results.

  • Latest release: v1.0.0

  • Disambiguation5/5

    The two tools have completely distinct purposes: 'fetch' retrieves specific content from a book using an epub URL, while 'search' performs library-wide queries for books. There is no overlap in functionality, making it impossible to confuse them.

    Naming Consistency5/5

    Both tool names follow a simple, consistent verb pattern ('fetch' and 'search') that clearly indicates their actions. The naming is straightforward and predictable across the set.

    Tool Count2/5

    With only 2 tools, this server feels severely under-scoped for managing an ebook library. Essential operations like adding books, updating metadata, deleting entries, or listing books are missing, making it incomplete for typical Calibre workflows.

    Completeness2/5

    The toolset is highly incomplete for ebook library management. While 'fetch' and 'search' are useful, there are significant gaps: no CRUD operations for books (create, read, update, delete), no library organization tools, and no metadata management beyond search. This will cause agent failures in common tasks.

  • Average 3/5 across 2 of 2 tools scored.

    See the Tool Scores section below for per-tool breakdowns.

    • No community issues in the last 6 months
    • No commit activity data available
    • No stable releases found
    • No critical vulnerability alerts
    • No high-severity vulnerability alerts
    • No code scanning findings
    • CI status not available

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How is the quality score calculated?

The overall quality score combines two components: Tool Definition Quality (70%) and Server Coherence (30%).

Tool Definition Quality measures how well each tool describes itself to AI agents. Every tool is scored 1–5 across six dimensions: Purpose Clarity (25%), Usage Guidelines (20%), Behavioral Transparency (20%), Parameter Semantics (15%), Conciseness & Structure (10%), and Contextual Completeness (10%). The server-level definition quality score is calculated as 60% mean TDQS + 40% minimum TDQS, so a single poorly described tool pulls the score down.

Server Coherence evaluates how well the tools work together as a set, scoring four dimensions equally: Disambiguation (can agents tell tools apart?), Naming Consistency, Tool Count Appropriateness, and Completeness (are there gaps in the tool surface?).

Tiers are derived from the overall score: A (≥3.5), B (≥3.0), C (≥2.0), D (≥1.0), F (<1.0). B and above is considered passing.

Tool Scores

  • Behavior2/5

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

    No annotations are provided, so the description carries the full burden. It states the tool fetches content but doesn't disclose behavioral traits such as whether it's read-only or mutative, what happens with invalid URLs, rate limits, or authentication needs. This is inadequate for a tool with zero annotation coverage.

    Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

    Conciseness5/5

    Is the description appropriately sized, front-loaded, and free of redundancy?

    The description is a single, efficient sentence that front-loads the purpose and key constraint ('epub:// URL'). There's no wasted text, making it appropriately sized and well-structured for quick understanding.

    Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

    Completeness2/5

    Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

    Given the tool's complexity (fetching content with a single parameter), lack of annotations, and no output schema, the description is incomplete. It doesn't explain what 'content' is returned (e.g., text, metadata), error handling, or other behavioral aspects needed for effective use.

    Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

    Parameters3/5

    Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

    The schema description coverage is 100%, with the parameter 'url' fully documented in the schema. The description adds minimal value by specifying 'epub:// URL from search results', which hints at the source but doesn't provide additional syntax or format details beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

    Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

    Purpose4/5

    Does the description clearly state what the tool does and how it differs from similar tools?

    The description clearly states the action ('fetch') and resource ('specific content from a book'), and specifies the required input format ('using epub:// URL'). However, it doesn't explicitly differentiate from the sibling 'search' tool, which likely returns URLs rather than content. This makes it clear but not fully sibling-distinctive.

    Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

    Usage Guidelines2/5

    Does the description explain when to use this tool, when not to, or what alternatives exist?

    The description provides no guidance on when to use this tool versus alternatives. It doesn't mention the sibling 'search' tool, prerequisites like needing a URL from search results, or any exclusions. This leaves the agent with minimal context for tool selection.

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

  • Behavior2/5

    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 the two search modes but doesn't describe important behavioral traits like whether this is a read-only operation, performance characteristics, error handling, or what happens when no results are found. For a search tool with zero annotation coverage, this leaves significant gaps.

    Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

    Conciseness4/5

    Is the description appropriately sized, front-loaded, and free of redundancy?

    The description is appropriately concise with two sentences that efficiently convey the core functionality. It's front-loaded with the main purpose and follows with search mode details. Every sentence serves a purpose without unnecessary elaboration.

    Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

    Completeness2/5

    Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

    Given the complexity of a search tool with 3 parameters, no annotations, and no output schema, the description is incomplete. It doesn't explain what results look like, how they're formatted, whether pagination is supported beyond the limit parameter, or what authentication/rate limits apply. The description should provide more context for effective tool use.

    Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

    Parameters3/5

    Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

    The description adds minimal value beyond the input schema, which has 100% coverage. It mentions 'full-text content search (default) and metadata search using field syntax' which provides some context for the query parameter, but doesn't add meaningful semantics beyond what's already documented in the schema descriptions for each parameter.

    Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

    Purpose4/5

    Does the description clearly state what the tool does and how it differs from similar tools?

    The description clearly states the tool's purpose: 'Search the Calibre ebook library' with specific capabilities (full-text content search and metadata search). It distinguishes the search function from the sibling 'fetch' tool by specifying search operations rather than retrieval. However, it doesn't explicitly differentiate from 'fetch' in terms of when to use each.

    Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

    Usage Guidelines3/5

    Does the description explain when to use this tool, when not to, or what alternatives exist?

    The description provides some usage context by mentioning 'default' full-text search and metadata search with field syntax, but it doesn't explicitly state when to use this tool versus the 'fetch' sibling or provide clear when/when-not guidance. The usage is implied rather than explicitly defined.

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

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